BOB ABERNETHY: And now our cover story: publicity for sex offenders. It's hard to think of any offense more difficult to forgive than sexual assault, especially on a child, but many offenders say they're being unfairly punished: once by the criminal justice system; a second time by their neighbors, particularly where the names and addresses of sexual offenders are made public. Do convicted sex offenders have rights to privacy? What are the rights of society to protect children? Lucky Severson reports on this conflict.

LUCKY SEVERSON: You might find Karen Meneke staring through the screen door of her comfortable Long Island home as if she is expecting trouble, although this hardly seems like a dangerous neighborhood.

Ms. KAREN MENEKE: In May, we found out that a sex offender is living on our block, and we weren't informed by the police.

SEVERSON: The sex offender grew up in this neighborhood and moved back in with his mom after serving time in jail. Like many neighbors here, Karen Meneke was worried about her two daughters.

Ms. MENEKE: And I was really upset, OK? And I didn't know what to do. So my neighbor called the advocate for Megan's Law in Suffolk County, Laura Ahearn.

Ms. LAURA AHEARN: (On telephone) So what's going on? Have you gotten a new portrait?

SEVERSON: Laura Ahearn is a woman to be reckoned with; a social worker turned crusader, determined to identify and stop sexual predators.

Ms. AHEARN: In any case where a sex offender is seriously sexually assaulting, changing a child's life forever, there is no excuse.

SEVERSON: She founded a watchdog group, like many that have sprung up around the country, called Parents for Megan's Law. That's the law Congress passed after two brutal and highly publicized murders of little girls: Polly Klaas by a convicted felon in California in 1993 and the rape and murder of seven-year-old Megan Kanka in 1994 by a twice-convicted pedophile. Megan's Law requires a state to notify communities when sex offenders move into a neighborhood. And now, with the Internet, sex offenders' addresses, their offenses, and sometimes their pictures are posted on Web sites around the country. But state laws vary, and New York had not notified Karen Meneke. She found out about the sex offender in her neighborhood from Laura Ahearn's Web site.

Ms. AHEARN: Right now we're -- we have about 1,000 per hour, people visiting the site.

SEVERSON: The neighbors held a town meeting to discuss their unwelcomed neighbor. They didn't know it, but he was there listening in.

Unidentified Man: One woman even asked, "How do we know if this person still looks the same way?" You know, they had my picture up on a screen. And I was sitting in the back going, "Lady, you don't even know I'm here now."

SEVERSON: The 51-year-old father was released after serving six months for deviant sexual intercourse with his 13-year-old daughter and sexually abusing his 16-year-old son.

Unidentified Man: You know, I thought my marriage was crumbling, and I involved my children in my needs, and it was totally wrong.

SEVERSON: Because he is considered a serious offender, his name will stay on a New York state registry for at least 10 years.

Unidentified Man: I've already been punished by the courts. I'm still being punished by the courts. Does society have a right to punish me, too?

SEVERSON: Megan's Law's supporters say crime sentences are too light and that high-risk offenders cannot be rehabilitated, but an increasing number of critics question the ethics and the fairness of the law. They say sex offenders are punished twice; that they are constantly harassed and driven underground, where they are more likely to offend again.

Unidentified Man: I'm worried that, you know, at some point my job could be threatened if this ever gets out. Web sites have my address, and I -- we get a lot of cars driving by very slowly, staring at me. It's like people driving by the "Amityville Horror." You know, 'Oh, my God, that's the place.'

Dr. ROBERT FREEMAN-LONGO (Therapist): The law feels good, it sounds good, but is it really doing the job it's supposed to do?

SEVERSON: Robert Freeman-Longo is an expert in the treatment of sexual abusers.

Dr. FREEMAN-LONGO: For the majority of cases I'm seeing now, you know, it's had devastating effects on their lives and the lives of others.

SEVERSON: In Texas, you can find information about sexual offenders on Texas-size billboards, and it is one of many states that now lists registries on the Internet.

This 16-year-old confessed to molesting his brother's three-year-old daughter.

Unidentified Teen: Since that day, you know, it's now like all my life has just gone downhill.