LINDSEY HILSUM: Jamkaran, the shrine to the 12th imam, the Mahdi. The faithful write their prayers. He is their most revered saint, their only hope. One day, they believe, he'll return to Earth through the well which lies under the postbox.
In the meantime, they mail him their wishes. One woman prays the Mahdi will cure her son's opium addiction. In the men's section, more prayers -- a terminally ill child, a daughter still unmarried, unemployment, all the problems of poverty.
Many mullahs say the well and postbox are mere superstition, but thousands of Iranians come to the Jamkaran shrine every Tuesday evening. They're looking for a sign that the Mahdi will return soon.
Now, it seems the Mahdi has become political. Iran's new president says he's a devotee of the 12th imam and of Jamkaran.
One of the first things Mahmoud Ahmadinejad did on becoming president was to allocate $17 million to this shrine to the 12th imam, the Mahdi. All Shias believe that one day the Mahdi will return, but some Iranians are beginning to worry that their new president is reorienting the country's politics towards that day.
Darkness falls and still the pilgrims come. They're warding off the evil eye. For eight years, Iran was run by reformists who talked of democracy and disparaged such religiosity, but the new president talks the language of the people.
Some are keen to praise him, provided they don't have to look a woman journalist in the eye.
MAN (Translated): Mr. Ahmadinejad is the only president in 28 years who came with a slogan of bringing justice, saying that he is one of us, cut from the same cloth. He proudly invokes the name of God the merciful, and after that he always prays for the coming of the Mahdi.
LINDSEY HILSUM: He repeated that prayer when he addressed the U.N. General assembly last September, calling on God to hasten the coming of the Mahdi.
A DVD circulating secretly in Tehran and on the Internet shows the president a few days later entering a house with a senior conservative ayatollah. They sit and drink tea in the traditional manner. What he says about his experiences in New York gives a rare insight into how Mr. Ahmadinejad really thinks.
PRESIDENT MAHMOUD AHMADINEJAD (Translated): On the last day when I was speaking before the assembly, one of our group told me that when I started to say "In the name of God the almighty and merciful," he saw a light around me, and I was placed inside this aura. I felt it myself.
I felt the atmosphere suddenly change, and for those 27 or 28 minutes, the leaders of the world did not blink. When I say they didn't bat an eyelid, I'm not exaggerating because I was looking at them. And they were rapt.
It seemed as if a hand was holding them there and had opened their eyes to receive the message from the Islamic republic.
LINDSEY HILSUM: The reformists are horrified that this is the image of Iran being seen around the world.
REZA KHATAMI, Opposition Leader: In the last eight years, the reformists tried to give a very clear sign to the world that Islam in Iran is not so fanatic. And I think the new government, they want to go back three decades -- and they not only want to go back themselves; they want to pull back the country three decades, so everybody now is worried about the future.
LINDSEY HILSUM: Happy landings. It's the annual day of the Basiij, a paramilitary organization meant to protect the country. Three decades ago, they were the vanguard of the Islamic revolution. Today, they're showing off their skills --
GROUP: Allah akbar!
LINDSEY HILSUM: -- and their air force. This is Mr. Ahmadinejad's power base, his enforcers amongst the population, although it looks as if not everyone's in step.
We caught up with the president and asked what he meant when he said Iranians should prepare for the return of the Mahdi. The reply: "They must be pure and devout."
Mr. Ahmadinejad shocked western governments when he said Israel should be wiped off the face of the earth. He used Basiij Day to send another hard-line message to Europe and America, the countries trying to prevent Iran from developing nuclear technology.
PRESIDENT MAHMOUD AHMADINEJAD (Translated): You whose arsenals are full of nuclear weapons, you who have used nuclear weapons this century against defenseless people and nations, you who used depleted uranium in the Iraq war, you whose arsenals are full of chemical and biological weapons, who are you to come out and say that you're suspicious of Iran's nuclear program?
LINDSEY HILSUM: A human chain symbolically protecting the country. The reformists fear the president's harsh words will lead to Iran being called up in front of the U.N. Security Council on suspicion of making a nuclear weapon.
MOHAMED ALI ABTAHI (Translated): We want nuclear technology to enhance Iran's standing in the world, but if that means we will have to sacrifice the power we already have because of sanctions or even more extreme measures against us, then in reality we will have gained the technology, but we won't have increased our power and influence at all.
LINDSEY HILSUM: The Bright Future Institute at Qom is devoted to the study of the Mahdi and other Messianic cults, they catalogue the literature and answer questions from the public sent in by e-mail, phone or letter.
The most common query is: How will we know that the Mahdi is about to return?
The children's books they design show what a wonderful world it will be afterwards. But just like fundamentalist Christians, Shias believe the messiah's second coming about be heralded by an apocalypse, war and chaos; they don't say it publicly but some Iranians worry that their new president has no fear of international turmoil, may think it's just a sign from God.