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>> Tonight on Frontline: David Coleman Headley... >> Headley was brilliant and evil at the same time.

>> ...an American raised in Pakistan... >> He changes his name to David Coleman Headley so that he can travel more easily.

>> ...recruited by Pakistani terrorists... >> A guy who's holding a US passport, Headley is a dream come true from the perspective of a terrorist group.

>> ...but also an informant for the DEA... >> He uses that to cover allegations of his extremism.

>> ...and the major force behind the most spectacular terrorattack since 9/11.

>> Mumbai has been hit and hit hard.

>> The attackers were well-armed and well-prepared.

>> David Coleman Headley, widely suspected to be a US double agent.

>> Tonight on Frontline, ProPublica reporter Sebastian Rotella investigates what the US knew about "A Perfect Terrorist."

>> Did they ask him about his work for the US government?

>> We were told by the USA, "That is not to be asked."

>> ROTELLA: The evening of November 26, 2008, was calm in the city of Lahore in eastern Pakistan.

In one neighborhood, a man was at home with his wife when he received a text on his phone.

He had been waiting for the message.

He was told, "Turn on your television."

>> Hours ago, terrorists launched a brazen attack.

>> The Indian city of Mumbai is in chaos following a series of terrorist attacks.

>> Mumbai's been hit and hit hard.

(gunfire) >> ROTELLA: 900 miles away in India, the most spectacular terror attack since 9/11 was underway.

>> You heard a big blast, right now, inside the Taj Hotel.

>> ROTELLA: The world watched as an icon of India was set ablaze, and civilians-- Indians and Westerners-- were methodically gunned down.

>> They wanted anyone with British or American passports.

>> I could see someone lifting up a gun, like that, and firing.

>> ROTELLA: With guns, grenades, and military precision, ten men were laying siege to the port city of Mumbai.

>> The attackers were well-armed and well-prepared to launch what some here are calling "India's 9/11."

>> ROTELLA: 166 people were killed.

Indian officials quickly connected the attackers to a militant Islamic group in Pakistan with ties to the ISI, the country's intelligence service.

But what they didn't know was that, for two years, an undercover operative had been casing the city, developing a blueprint for terror.

His name: David Coleman Headley.

He'd been chosen for the job because he had the perfect cover; he was an American.

For the past year, I've been on the trail of David Coleman Headley, investigating his rise from small-time drug smuggler to international terrorist and spy.

I started here in Chicago, where, in 2008, Headley had moved his Pakistani wife and four children.

They lived on the North Side, near Headley's old friend, a man named Tahawwur Rana.

(doorbell rings) Mrs. Rana, how are you?

If you could tell me what you know about how they met?

I talked with Rana's wife.

>> My husband, he told me he was his class fellow.

>> ROTELLA: Headley and Rana became close in the 1970s... >> This is my husband.

>> ROTELLA: ...growing up outside of Islamabad.

>> This is Dave.

>> ROTELLA: David Coleman Headley.

>> Mm-hmm.

>> ROTELLA: The Ranas considered Headley family.

>> Dave was very, very nice.

He called me "sister," and he said, "You are my sister."

And that was a very good thing.

And my kids also started calling him, like, "Special Uncle."

"He is the best."

He would take them to Chuck E. Cheese, this and that.

He knew what kids like.

>> ROTELLA: For years, the Ranas had been operating an immigration company.

It specialized in getting foreign professionals US worker visas.

Your husband worked in here, then?

>> My husband, he... >> ROTELLA: Headley used the business as a front when he was plotting the attacks in Mumbai.

Did David Coleman Headley ever come to this office?

>> Yes.

He was coming, but he was not doing anything.

He just came, like, four or five times.

Because he was not working in this office.

He was working at Mumbai office.

>> ROTELLA: At Mumbai.

>> Yes.

>> ROTELLA: He'd used it as a cover for illegal activity as far back as 1997, telling people he worked here when he was really smuggling drugs.

>> And now, he's involved in this Mumbai attack.

So many innocent people were killed in that.

I mean, I cannot believe it because, you know, David was not a person who can do this.

David Headley is insane.

That's it.

I can say only this thing.

No person with a brain can do these things.

He's insane.

He don't know what he's doing.

>> ROTELLA: David Coleman Headley is not his given name.

He was born Daood Gilani in Washington, DC, in 1960.

His father was a well-known Pakistani broadcaster.

His mother, Serrill Headley, a daughter of Philadelphia high society.

The family moved to Pakistan early in the boy's life.

One neighbor was this man, Chand Bhai, who says he's known Gilani since that time.

>> ROTELLA: But soon, the parents divorced, the clash of American and Pakistani culture at the heart of the breakup.

His father remarried; his mother returned to America, forced to leave her son.

Daood grew up in private military schools, where duty to flag and country was instilled.

>> Every morning, at the Habib Public School, hundreds of boys line up to pay tribute to the flag.

>> ROTELLA: He says he was a student here when Pakistan suffered a humiliating defeat in a war with India.

Stray bombs fell on the school, killing two people.

>> ROTELLA: As a teenager, Gilani attended the Hasan Abdal cadet college, where he first met Tahawwur Rana.

The two young friends grew up with the privileges of the Pakistani elite.

>> They are like the cream of Pakistan's people, you know.

>> ROTELLA: So, what's the reputation of his family in Pakistan?

>> His father was rich and well-known man.

I mean, he's one of the persons that 90% of people know in Pakistan.

>> ROTELLA: At home, Daood didn't get along with his stepmother, and, at age 17, he sought the help of his true mother, Serrill Headley.

She brought him back to the US, to Philadelphia, where she owned this bar, the Khyber Pass.

Here, Daood met American culture head-on... ...thanks in part to his mother.

>> Hello, everybody, and welcome to the Khyber Pass pub on Second and Chestnut Streets.

We are live tonight.

>> ROTELLA: She was a fixture in the Philadelphia social scene, a local character known for her bar... >> The Khyber Pass pub is ten years old.

>> ROTELLA: ...and her colorful past... >> You might call her a special owner.

>> She is a Delaware Valley native, but ten years ago, her story read like a Mid-Eastern spy novel.

>> ROTELLA: ...a past she happily advertised-- life in Pakistan, false charges of espionage, her life under threat, and escape through the bar's namesake.

When her 17-year-old son arrived from Pakistan, it only added to the bar's mystique.

There, they called him "the prince," but a prince who had a dark side.

Daood Gilani, age 23.

Handsome, self-assured, and within two years of these images being taken, a heroin addict and a budding drug smuggler.

It's hard to pinpoint exactly when Gilani stepped onto the path that eventually led to the Mumbai attacks.

Headley has now moved overseas to Philadelphia, but he's visiting Pakistan and apparently already has this drug habit, has already gotten into a life of drugs.

So, he goes up to the tribal areas with Rana, his best friend, because Rana has a military ID, and Headley is concerned about checkpoints or being stopped.

And he knows if that happens and Rana can show his military ID, they're likely not to be searched, unbeknownst to Rana that he's going up there to get drugs.

So he uses him essentially as cover.

And they make it back, but a couple days after he returns, he gets arrested in a hotel with a woman, and there's some kind of incident.

Whether it's an overdose or she gets sick, there's something having to do with drugs or drug use that causes a commotion and draws the attention of the authorities, and Headley gets arrested for drug possession.

But somehow, Gilani got away with it.

He gamed the system and survived.

Then, in 1988, a turning point.

He got caught in transit by US drug agents, two kilos of Pakistani heroin tucked into the false bottom of his suitcase.

On the spot, he agreed to cooperate with the DEA, the Drug Enforcement Administration.

One partner got ten years, the other got eight.

Gilani only got four.

>> He just turns around immediately and betrays everybody when it's convenient for him.

Basically, it's survival for himself.

>> ROTELLA: Gilani did his time.

He moved to New York, opening a video store.

But three years later, he was arrested again for drug smuggling.

This time, he hired a lawyer to negotiate terms.

Pleasure.

>> Likewise.

>> ROTELLA: Thanks for taking the Saturday.

>> That's all right.

I remember him being highly intelligent, understood what his situation was, had a clear idea of what he wanted to do.

>> ROTELLA: Which was?

>> What he wanted was to cooperate with the government, which he'd done previously, and he also wanted to be out on bail.

>> ROTELLA: He did cooperate.

He became a DEA informant.

His job was to set up his sources in Pakistan.

The DEA even let him out on bail and sent him there to maintain his cover.

>> That happens because there was a lot of suspicion that maybe he was simply trying to set people up.

But if he had the ability to physically travel all the way to Pakistan and show his face, that would allay concerns.

>> ROTELLA: So what's to stop him in terms of the amount of trust they had in him?

I mean, he could theoretically just stay there and not come back, right?

>> Often, what you'll see is the relationship between informant and agent sort of develops, and time goes by, there's a level of trust that gets established.

>> ROTELLA: The DEA says it funded only one of Gilani's trips to Pakistan.

But while on probation, he began traveling back and forth, often without his handlers' knowledge.

On one trip, he came to Lahore and attended this mosque, known for its support of the Islamic militant group Lashkar-e-Taiba.

For decades, Lashkar has been fighting Pakistan's guerilla war against India in the disputed region of Kashmir.

He met Lashkar's leader, Hafiz Saeed, on another trip and was moved by his militant call to action.

>> He decides to actually join Lashkar-e-Taiba while he's still a resource for the DEA.

>> ROTELLA: When he wasn't in Pakistan, Daood Gilani lived here, on Manhattan's Upper West Side.

I spoke with a close friend of his who says Gilani's life was in flux.

He was married to a woman in Pakistan and seeing women in America.

But he'd given up drugs and was immersing himself in radical Islam.

And then... ...the day that changed everything and everyone, including Daood Gilani.

The next day, his DEA handlers called him.

They needed more than just a drug informant.

Now, they wanted to know about terrorists.

He did it willingly, gathering intelligence on extremists in New York and calling sources in Pakistan.

But he revealed other views to an ex-girlfriend soon after 9/11.

She then told her friend, Terry O'Donnell.

You guys were sitting in a bar, right?

You and her and... >> We were standing.

>> ROTELLA: You were standing, all right.

You, her and somebody else?

>> Another waiter, but he was kind of hitting on a girl two stools down.

Sportscenter was on here and Channel 7 News was on here, and it was about 11:30 at night and the news was on.

She said, "Well, you know, my boyfriend said "America got what it deserved, you know.

I mean, we're not innocent in this."

And I was like, "Wow, that's a pretty insensitive thing to say, especially two, two-and-a-half weeks after this happened."

And then she went on and said, "He was happy to see it happen, and he got off on watching the news over and over again."

I was conflicted whether I should say something to the... the cops.

I don't know, maybe this guy's just all talk, he's just saying this.

He's an ass (bleep), he's entitled to his opinion.

Does this mean I should call the authorities on him, the police?

And then, you know, you look downtown and you're like, "I don't know, maybe this guy is for real."

Well, look what happened downtown two weeks ago.

>> ROTELLA: Tipped off by O'Donnell, the FBI questioned Gilani about his statements.

With DEA agents in the room, he denied it all.

>> In October of 2001, he was confronted by FBI agents.

He said, "Oh, you think I'm an extremist?

"You think I'm interested in jihad?

"Don't forget, I'm...

I'm working for the US government.

"You've got it all wrong.

"I'm one of the good guys.

I'm working for the DEA."

And he uses that information to cover allegations of his extremism.

>> ROTELLA: He talked his way out of it.

Soon after, at a hastily called hearing, a US prosecutor asked a judge to end Gilani's probation early-- a highly unusual move.

>> It's the only occasion I can recall it ever happening.

>> ROTELLA: Howard Leader was there for Gilani.

He says US officials seemed to want to rush his client to Pakistan as an operative in the new war on terror.

>> I think that he was going to go back to Pakistan with a view towards meeting with or gathering whatever information he could that might be useful to the US government regarding certain extremist elements there.

>> ROTELLA: What happened to Gilani next is unclear.

Some US and foreign officials insist he became an American intelligence operative, but off the books.

Gilani would later say he worked with the DEA for another year.

But a senior DEA official told me the agency stopped working with him after the probation hearing.

What is clear: in early 2002, Gilani began his training with Lashkar.

>> Headley would've started out with a religious indoctrination, and, several months later, he would have gone on and done the general training, the three weeks' light weapons.

And sometime later, he went on and he did the specialized training.

That's the hand-to-hand combat, guerilla warfare training, the regular warfare training.

>> ROTELLA: For a long time, many Western officials didn't consider Lashkar a serious international threat, like al Qaeda.

The group was mostly known for engaging in a holy war, a jihad, against India.

>> Lashkar began launching these raids by a small number of people in Kashmir.

And sometimes, these were hit-and-run attacks like you would normally get in battle.

But quite often, what they did is they would hit and then they would stay.

They didn't run, they hunkered down.

And it was sort of this stronghold option.

And the idea was they would fight for hours upon hours.

Sometimes 20, 25, 30 hours these battles would go on.

>> ROTELLA: Weeks before Headley started his training, and in the wake of 9/11, the US officially designated Lashkar as a foreign terrorist organization.

But Gilani didn't hide his Lashkar training, at least not from those he was closest to, like his mother.

Serrill Headley moved to this house in the small town of Oxford, Pennsylvania, in the late 1990s.

On many days, she would come here for coffee to talk with Phyllis Keith, who owns the Morning Glories caf\ with her husband, Michael.

>> She came in regularly-- I'd say maybe two, sometimes three times a day.

>> ROTELLA: And at some point, some of the stuff she said started to pique your interest.

Can you tell me about that?

>> What I remember is, it was later in the day, and there weren't any other customers in the shop.

And she sat down and said, "I think my son might be involved with training camps in Pakistan."

Just pretty much straight-out said that.

>> The impression that I got from her is that he was in and out of the country pretty regularly, and at times, she wouldn't know where he was.

>> At that point in time, they were saying, you know, "If you hear something, you see something that makes you suspicious..." And one night, I went home from work, got out the phone book, looked up the FBI, and gave them a call.

>> ROTELLA: You say the conversation lasted how long?

>> I don't know.

Five minutes?

>> ROTELLA: Did you hear from them again?

>> No.

>> ROTELLA: As Daood Gilani honed his skills in Lashkar-e-Taiba's training camps, he was becoming a Pakistani warrior.

And after three years, he wanted to fight in Kashmir, but one commander in Lashkar had other plans for him.

His name: Sajid Mir, a man who would become known as a mastermind behind the Mumbai attacks.

Details about him are murky.

What we do know is he's young, in his 30s.

He speaks fluent English.

>> Sajid Mir, I'd see him whenever he came round.

>> ROTELLA: And he led the recruitment of Western operatives, pushing Lashkar's jihad beyond India.

>> And everyone had demands on his time-- the different foreigners staying there, myself... >> ROTELLA: One of Mir's recruits was Charles Wardle from New Zealand.

In late 2001, he was a young drifter traveling to some of the world's most dangerous places.

In Pakistan, he met Sajid Mir, who persuaded him to convert to Islam and become an operative for Lashkar.

Do you suspect, perhaps, that Sajid Mir had in mind for you to do something comparable to David Coleman Headley?

>> Yeah.

That's the impression that I got, that I would be returning to my country, where I would use my training.

>> ROTELLA: Use your training to do what?

>> I can only guess, but explosives training.

I guess he would have had a target in mind.

>> ROTELLA: Did he ever discuss any views of the Pakistani government, the Pakistani military, of the intelligence service?

>> Well, I know that some of the Lashkar-e-Taiba training was conducted with the military.

They have a very close relationship with the Pakistani military.

>> ROTELLA: Wardle says Sajid Mir had unusual clout.

>> Sajid Mir was, you know, an authority and a power in his own right in Lashkar-e-Taiba, and he could pretty much do whatever he wanted.

I don't know what his limitations were, but my impression was he didn't have to pay too much attention to Lashkar-e-Taiba hierarchy.

>> ROTELLA: Mir has been known to Western investigators for almost a decade.

France even convicted him in absentia for a bomb plot in 2007.

To this day, investigators say he is untouchable, protected by the most powerful branch of the Pakistani military: the Inter-Services Intelligence Directorate, the ISI.

>> There are a lot of questions about Sajid Mir.

Is he really an ISI person who is within Lashkar-e-Taiba, or is he a Lashkar-e-Taiba person who was trained by the military in the background?

It doesn't matter.

It doesn't matter because, in a sense, Lashkar-e-Taiba was a proxy of the Inter-Services Intelligence Directorate, and very much under their control.

>> ROTELLA: After three years of training with Lashkar, Daood Gilani was ready to join the jihad.

In 2005, he lobbied to fight in Kashmir, but Sajid Mir had a different plan.

That Fall, it was revealed: Mumbai.

The details were sketchy, but filling them out would be Gilani's job.

>> Lashkar-e-Taiba is a terrorist organization, so it trained people to kill.

They don't do logistics very well.

And at that point, I'm not sure that Headley would have been able to carry it out yet.

He needed something else.

He needed real training in espionage.

>> ROTELLA: Gilani would later reveal the help came from the ISI.

Word of Sajid Mir's new American recruit reached an officer in the intelligence agency, Major Iqbal.

"Iqbal" is probably an alias.

The FBI and Interpol have him listed as wanted, but they don't even have his picture.

Gilani was to report to Iqbal and Mir separately so the ISI could maintain deniability.

>> Iqbal delegates a non-commissioned officer to give Headley additional training, in terms of espionage.

>> How to evaluate a building, security of a building, security of a place, basically writing casing reports, what's important.

So, all of this is very much a preparation for his real mission, which is casing Mumbai for a potential attack later on.

>> ROTELLA: The Pakistani military refused to comment to Frontline and ProPublica aboutthe case and denied any role in the Mumbai attack.

In August 2005, Gilani returned to New York to sell his video store and spend time with his Canadian-born second wife.

They were having trouble.

This used to be Fliks Video, which was the video store that Headley owned for a number of years.

He comes back here from Pakistan and meets with his wife at this store, and they have an argument about money.

And the allegation that the wife made at the time was that he got angry and he hit her.

Apparently, she said, he backhanded her with his cell phone in his hand.

She had Gilani arrested for assault, but the case was ultimately dropped.

She also reported him to the FBI.

She met with agents three times and told them in detail about Lashkar, about the training camps, even that Gilani had bought night-vision goggles.

You know, this incident that happened here, with the combination of the domestic assault allegation and the tip to the FBI, represented a golden opportunity to find out who he was.

This was a serious moment, like a hinge moment in his trajectory into terrorism.

An FBI agent called Gilani's former handler at the DEA, but Gilani wasn't questioned.

Officials have told me his past as an informant caused the FBI to drop the inquiry.

It was as if Gilani could get away with anything.

He escaped detection and came here to Philadelphia with one job to do.

Good morning.

>> Good morning, how are you?

>> ROTELLA: Daood Gilani was about to disappear.

So, I was looking for a record of a name change.

Gilani, G-I-L... >> He was born Daood Gilani.

He comes back to the US, and he changes his name... >> ROTELLA: It became David Coleman Headley.

>> Got it.

>> ...to David Coleman Headley, so that he can travel more easily, more covertly.

It's at this stage that Sajid Mir and Iqbal begin sending him to India.

>> ROTELLA: So now, you've got a guy who's just gone through all this Lashkar training, more than most Lashkar militants do, and now he's done this additional espionage, pure espionage training with the ISI.

What do these two organizations see in this guy, and how does he compare to other jihadis of the many you've looked at?

>> David Coleman Headley is, you know, a gold mine for both an intelligence service and a militant organization that is looking to gather information.

>> ROTELLA: Over the course of 20 months, Headley traveled in and out of India at least five times, staying weeks or months at a stretch.

Each visit, he advanced the attack plan.

I came here to retrace his steps.

>> Investigative sources say Headley surveyed all the 26/11 targets.

>> The game is over for Lashkar operative David Coleman Headley.

A day after the Americans... >> ROTELLA: Even Mumbai's monsoons can't wash away the infamy of David Coleman Headley.

>> He revealed how he attended various LET camps.

>> His love for luxury made him a terrorist by profession.

>> ROTELLA: Here, he's a household name... >> As we know, David Headley is an undercover agent working for the American agencies... >> ROTELLA: ...as synonymous to the November 2008 attacks as bin Laden is to 9/11 for Americans.

>> Is America hiding more than it's revealing about David Headley?

>> David Coleman Headley, widely suspected to be a US double-agent.

>> ROTELLA: But with an added horror: he lived amongst those he planned to kill, always maintaining his cover, befriending the unwitting.

(high-pitched music playing in elevator) I went to the apartment complex where he had lived... Got to love that music, huh?

...to walk the halls where he had walked, and to try to talk with the people who might have known him.

We're sorry to barge in on you on a Sunday.

So, did you ever see David Coleman Headley?

>> No, I wouldn't even know it's him.

I wouldn't even know it's him.

>> ROTELLA: But everyone who had known him now seems to want to forget about it, including this woman who rented him an apartment.

>> (speaking local language) >> Just for two minutes?

Ma'am, we've come all the way from America.

>> Okay.

>> Nobody who knew Headley wants to talk about him.

You get doors slammed in your face.

It's almost as if they feel just having known him taints them by association with this extraordinary evil.

>> ROTELLA: Ask him if he ever remembers seeing David Coleman Headley.

(woman translates) He got to know the city.

He walked its streets, took its taxis, got to know people.

(dialing number on phone) >> Yes, Sebastian, brother.

>> ROTELLA: How you doing?

>> Good, good, brother.

You tell me.

>> ROTELLA: He even made friends with a B-movie actor named Rahul Bhatt... >> It's not that I didn't want to do it.

>> ROTELLA: ...who would only talk to me if I paid him.

>> You've got to do something for me, Sebastian.

>> ROTELLA: I refused.

>> Nobody else knew Headley the way I knew him.

>> ROTELLA: He introduced Headley to Mumbai's party scene.

>> ROTELLA: Devon Bharti is the commissioner of investigations for the Mumbai police.

>> After this place, they took a left turn.

>> ROTELLA: He questioned the people who knew Headley, like his secretary.

Headley hired her for the Mumbai office of the immigration company owned by his friend, Rana.

The business was here, but it was just a front.

>> ROTELLA: Headley had succeeded on his first mission: insinuating himself in Mumbai.

>> You know, if you go through old Bollywood films, there's always one white guy who is inflicting some vile hardship on poor peasants or, you know, innocent street pavement dwellers and stuff.

And we all grew up with that, that one evil guy who always wore a suit and hung around at expensive hotels.

David Headley is that guy.

>> ROTELLA: The Taj Mahal palace, the five-star hotel built in 1903-- a symbol of India and Western-style luxury.

Headley walked into the Taj on his first visit to Mumbai in September 2006.

From the start, Sajid Mir and Major Iqbal knew this would be ground zero of a Mumbai attack.

Headley stayed here occasionally, casing the joint.

The Taj was rebuilt after the attacks.

It's more opulent and more secure, a real fortress.

I wanted to see the place through Headley's eyes.

It's such a grim image of him coming here.

I can just imagine him being charming and friendly and taking full advantage of everything.

And we know specifically because of the credit card charges, he went to the Montblanc store and got himself a nice pen.

He went and had breakfast in the Sea Lounge with the wonderful view of the water.

And the whole time he's sizing it up, and he's working the conference rooms and he's videotaping, and he's just assembling all this information.

That he's going to use this place, enjoy it, live like this jet-setting type of guy that he is, and then he's going to be the engineer of its destruction.

Headley returned to Lahore from his first reconnaissance trip in late 2006.

His status in Lashkar had been elevated.

He was the American operative who did things nobody else could.

>> What you see in the Headley case is a constancy.

Whether he's a drug dealer, whether he works for the DEA, Lashkar-e-Taiba, or ISI, you see the same pattern all over.

>> ROTELLA: And that pattern is?

>> The pattern is risk-taking.

He wants to live for the moment.

He is not above taking crazy risks, such as always going back and forth between Pakistan and India.

It's almost like he's taunting people, showing them, you know, he's great.

He's got numerous wives, girlfriends on the side.

He loves the game.

He loves the game.

>> ROTELLA: Already married to two women, Headley decided to marry again, to a Moroccan named Faiza.

>> ROTELLA: She was fiercely independent, not a devout Muslim.

A med student, she wore Western clothes and partied with Headley's old friend, Chand Bhai.

He said Headley wanted a more traditional Muslim wife.

So he wanted her to wear those?

>> ROTELLA: She changed for him, but the marriage didn't work.

Headley put off telling his first wife about her.

Faiza felt she was being treated as a mistress, and she was left alone for months while he was in Mumbai.

Her anger led to what happened next.

She goes to the US embassy in Islamabad and warns them about her husband's extremist activities just as the Mumbai plot is really gathering momentum, the reconnaissance and the preparation.

>> That's right.

They must have had a disagreement.

She... you know, she's short-fused.

She goes to denounce him and... and mentions that he was trained by Lashkar-e-Taiba, he's really a terrorist.

And nothing happens.

>> ROTELLA: Perhaps most surprising, Faiza revealed to the US embassy officials that she and Headley had spent their honeymoon at the Taj Hotel the year before.

In combination with her other charges, that could have led investigators directly to Headley's work for Lashkar.

Alarming and detailed accusations were piling up.

>> His wife says he's involved in something.

You look at him for a week or a month and you can't find anything interesting.

There's 72 other active investigations going on in your office.

I think people are too quick in all these cases when they look at the individual case and say, "Hey, you should have known."

When, in fact, you're not looking at an individual case; you're looking at 6,000, saying, "I can't afford to prioritize this guy "when I've got 72 other knowns "that are really taking our resources and that merit further investigation."

>> ROTELLA: But the US did collect enough intelligence to send a series of warnings in 2008 to India about a potential attack in Mumbai, including on the Taj Hotel.

>> We got warnings that there was likely to be an attack in Mumbai.

The Taj Hotel was very specific.

But it's like any other thing-- you put an alert, people will wait for 15 days of alert or 30 days of alert, and then nothing happens.

>> ROTELLA: GK Pillai led the department overseeing India's security agencies.

He believes that David Headley must have been a source of that information, but the US never let on.

>> If the Americans had just told us once, "Look, we've got this guy, he's coming in.

"We have a little bit of a suspicion about this guy, we just bring him to your notice."

And that was not done.

>> ROTELLA: Given that you were getting these warnings, why do you think that the Americans just didn't tell you about the potential danger from Headley in that period?

>> I can only say that it is because the information that David Headley was perhaps providing to the Americans proved useful enough that they were willing to overlook and keep this under wraps, because he was useful to them.

>> ROTELLA: So just to be clear, you feel, at this point, that Headley wasn't just working for the ISI in those months leading up to 2008; you feel he was working for someone else.

>> David Coleman Headley, in my opinion, was a double agent, was working for both the US and for Lashkar and the ISI.

>> ROTELLA: US officials deny that Headley was a double agent or that they knew he was involved in plotting the attacks.

They say he simply slipped through the cracks.

Three counter-terror sources have told me that there is more to the story.

They say US agencies didn't realize Headley's central role in the plot at the time, but did pick up fragments of intelligence about him.

In fact, they say that information contributed to the warnings to India.

Frontline and ProPublica repeatedly asked US officials to discuss the case on camera, but they declined.

Early in Headley's reconnaissance, his handlers had a limited goal.

>> A one- to two-person attack during a software conference at the Taj Mahal Hotel.

They still don't have a date set.

They're gathering more information.

But over time, what happens is Headley is being asked to look at more and more targets.

And what starts out as this one- to two-person hit and run attack against the Taj Mahal Hotel becomes this ten-person, multiple-target attack of the kind that Lashkar-e-Taiba has never launched before.

>> ROTELLA: Headley's reports seemed to embolden them.

By early summer 2008, a date was set for the attack.

And another important decision: the attackers would arrive by boat.

David Headley comes here, and one of the crucial roles he plays is in setting up a maritime attack, which is the hardest kind of terrorist attack.

Having the gunmen arrive by sea is ten times harder than having them arrive any other way.

He took boat tours from here.

He hired a fisherman to take him around.

And what he was looking for was the best approach and the best landing site.

Headley scoured the city, searching by car and boat.

And then he found the perfect spot: a fishermen's slum.

It's a pocket of poverty amid wealth, its beach used as a public sewer.

Here he saw a strategic landing site.

A main thoroughfare runs nearby.

Headley brought a GPS unit to map it out.

He comes here, he plots the GPS coordinates for this landing spot.

This route from Karachi to Mumbai had been plotted out by GPS.

This is the route, this is where we are right here.

It's all about the attackers themselves knowing where they're going to attack because these guys have never been here.

With a video camera, Headley traced the routes for the attack.

The Taj Mahal Hotel, about eight blocks east.

Two blocks closer was the Leopold Caf\.

Just around the seawall was the Oberoi Hotel.

And then, there was the busiest rail station in Mumbai.

Headley came to this station, walked on these platforms, sizing up the station, but first as a place for escape.

The original plan was for the attackers to come to this station and use the trains for a getaway.

Then, the plot evolved.

As it gets closer to the time of the attack, his handlers tell him, "No, no one's escaping.

These guys are going to fight to the death."

And Headley comes back, now looking at this station as a target, a place where they could kill a lot of people in a very short period of time.

An intelligence source gave me this photo.

It was taken July 1, 2008, upon his arrival at Mumbai's airport for his last reconnaissance.

He had been in Pakistan just before, briefing Major Iqbal and Sajid Mir, separately, as always.

He'd been given final instructions.

Headley revisited the attack targets one last time.

And then, he bought sacred Hindu bracelets.

>> ROTELLA: There was one more target to pinpoint.

Hidden in the back streets, just a few minutes' walk from the Taj Hotel-- Chabad House, a synagogue and hostel run by an American rabbi and his wife.

Major Iqbal chose the target.

His objective: the global jihad against Jews and Americans.

Headley had his GPS unit with him.

He input the location for the attackers, and, with that, his job in Mumbai was done.

>> This is possibly the most well-coordinated attack... >> ... attackers were captured on closed-circuit television... >> Officials described this as a professional and highly coordinated terrorist... >> ...explosives, some weapons they were able to lock down.

>> Teams of gunmen fanned out across the city.

>> There were people trapped in that building.

There are people still in this Taj Hotel.

>> This is a huge, massive fire that is on top of the Taj Hotel.

>> ...the Taj Hotel, Oberoi Hotel, Caf\ Leopold... >> ...train station... >> India has seen terrorism before, but nothing that would have required this level of planning and coordination.

>> At least 150 people have been killed.

>> One captured gunman is Pakistani.

>> 24 hours after these multi-pronged coordinated attacks began, this crisis is still going on.

>> A Jewish community center was attacked, the Israeli family taken hostage.

>> There's thought to be one to three gunmen inside.

>> India's elite commandos took control of a Jewish community center.

>> ROTELLA: Chabad House is not easy to find, but Headley's GPS had guided two of the attackers to its location.

The building is just a shell of what it once was, still pockmarked from the bullets and RPGs.

The attackers took hostages.

This began a three-day siege.

>> They had a lot of ammunition, and they kept on going for a while.

>> ROTELLA: Moshe Holtzberg's brother, Rabbi Gavriel Holtzberg, and his wife Rivka were among the first to die.

>> This is where they found my brother and his wife, lying over here.

>> ROTELLA: The police were able to intercept the attackers' cell phone calls.

This is when they overheard the conversation with one of the hostages.

>> ROTELLA: It was Sajid Mir, directing the siege from Karachi.

>> ROTELLA: He wanted to bargain for his wounded attacker.

He reassured Norma.

>> ROTELLA: The prisoner swap didn't happen.

Then, another call from Sajid Mir.

>> ROTELLA: This time, he's speaking in Urdu.

(gunshot) >> ROTELLA: David Coleman Headley had watched it all play out from his home in Lahore.

He was already thinking of his next mission.

Just a month before, he had visitors, two men he had never seen before in the same room: his handlers, Sajid Mir and Major Iqbal.

They had a new job for Headley-- to take their holy war to the heart of Europe.

These images are of Copenhagen, seen through the eyes of David Coleman Headley.

Video camera in hand, he came here to do reconnaissance.

>> Hotel D'angleterre.

>> ROTELLA: He acted like a tourist, recording his trip and narrating the images along the way.

>> French Embassy.

>> ROTELLA: But his true intent was to case the city and this newspaper, Jyllands-Posten.

Four years before, it caused outrage across the Muslim world by publishing 12 cartoons of the prophet Muhammad.

The plan was for Headley to get inside the newspaper to plot its destruction.

Headley would take two trips to Copenhagen in 2009.

But between the two, he changed allegiances.

Back in Pakistan, his sponsors were under suspicion after the Mumbai attacks.

Sajid Mir and Major Iqbal called off the Copenhagen plot.

They told Headley to lay low, but he went looking for a new sponsor instead.

He found one, a notorious terrorist named Ilyas Kashmiri, who has since been killed by a US drone strike.

Headley was now working for al Qaeda, which paid for his second trip.

>> The guard of the palace.

>> ROTELLA: It's very chilling, you know, because Headley gathers all this information-- the videotape, the notes-- and he goes back to Pakistan, and he meets with one of the most fearsome terrorists in the world right now, Ilyas Kashmiri.

And they have a detailed conversation about how this plot would go down.

It's a Mumbai-style attack.

Three or four attackers with automatic weapons would go in and take hostages but add a wrinkle, which is the beheading of the hostages.

Kashmiri says, "You shoot the hostages first.

"It makes it easier to behead them.

You behead them, and you throw the heads out the window."

Why?

Of course, for the shock and the awe and the terror.

This would be an international spectacle, here in the heart of Denmark, that would be seen by the world.

With his new al Qaeda connection, Headley ended up meeting with extremists who were under surveillance.

In the summer of 2009, Danish intelligence shadowed his every step.

Now, the FBI was watching him, too, from when he returned to Chicago in August until one day when he went to the airport.

He was on his way back to Pakistan.

In his bag he was carrying his Denmark surveillance footage.

October 9, 2009: Here at Chicago's O'Hare airport, federal agents arrested Headley.

>> ROTELLA: Facing charges for his role in the Mumbai attacks and the Denmark plot, Headley knew exactly what he had to do to avoid the death penalty.

He gave up unprecedented evidence about the ISI, Lashkar, and al Qaeda, but they wanted more.

>> ROTELLA: Sajid Mir.

Headley tried to lure Sajid Mir out of Pakistan.

It didn't work.

And so, after two weeks of interrogation... >> ROTELLA: ...Headley turned on the person he knew he could deliver.

>> Before we ask you any questions, you must understand your rights.

>> ROTELLA: Tahawwur Rana... >> You have the right to remain silent.

>> ROTELLA: ...His old friend from high school.

>> Anything you say can be used against you in court.

>> ROTELLA: Headley told the FBI Rana had been his accomplice... >> You have the right to talk to a lawyer.

>> ROTELLA: ...That Rana had provided Headley with a business cover.

And, as in the past, Headley began working the angles.

>> ROTELLA: He agreed to a plea bargain.

>> ROTELLA: He'd escaped the death penalty... >> ROTELLA: ...and saved his life.

>> Frontline continues online.

Explore David Headley's life through never-before-seen photos.

Read more from ProPublica reporter Sebastian Rotella about Lashkar-e-Taiba, the ISI, and Headley.

>> Headley figured out every step of the attack.

>> Find out what a top Indian investigator uncovered about the attacks.

>> Look, terrorists were given Indian identity cards.

>> And learn about efforts to rebuild Chabad House.

Follow Frontline on Facebook and Twitter or tell us what you think at pbs.org.

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