For more than two decades, John Walsh has been hunting the country's most dangerous criminals. At the helm of the show "America's Most Wanted," Walsh has helped put more than 1,000 fugitives -- serial killers, rapists and child abductors -- behind bars.
"I have caught some of the worst of the worst," he said. "We have caught 17 guys off the FBI's 10 Most Wanted [List]."
"Nightline" accompanied Walsh behind the scenes of his show, shooting on location near San Francisco, where he's on the trail of an alleged gangland killer.
The murder of Charles "CJ" Davis has had little media coverage, but Walsh turns cases such as this one into national stories. From Elizabeth Smart to Jaycee Dugard, whose case he first highlighted in 1991 -- just four days after she was abducted.
"I really think it's a miracle that Jaycee Dugard was found after 18 years," Walsh said. "I've been involved in some long-running cases...but for Jaycee Dugard to be found alive and healthy with two children fathered by her abductor, kidnapper, rapist -- a guy with a rap sheet that long that shouldn't have been found on the street, it's a miracle. It's a wonderful, wonderful ending to a really sad story."
Behind Walsh's anti-crime activism is his own tragic story -- one without the "wonderful" ending.
In July 1981, his 6-year-old son Adam was abducted from a shopping mall in Florida. John and his wife Reve desperately searched for Adam, but their worst fears were realized when Adam's severed head was found in a canal two weeks later. The rest of his body was never recovered.
"I'll always be the parent of a murdered child," Walsh told "Nightline." "Adam will always be in my mind. Your heart is broken. It doesn't matter if it was six months ago or 27 years ago. Your heart is broken. People deal with it differently. Some descend into hell in different ways and you live in that hell."
Adam's murder became one of the most infamous crimes against a child in America. And Walsh used his son's death to raise awareness for missing children across the country, creating the National Center of Missing and Exploited Children. He became a public face of the missing children movement. FOX asked Walsh to host "America's Most Wanted" in 1988, a program that prominently features cases in which children are harmed or missing.
To critics who label him a "fear mongerer," Walsh said that he considers his job "an obligation."
"I believe that knowledge is power. I truly believe that people watch too much TV and think there is going to be that superhero who is going to come in and stop this and that it can't happen to you," Walsh said. "If you spent one day with me, and saw how average crimes affect people in the United States. ...I don't believe in paranoia, I don't believe in fear mongering, I believe we have an obligation to tell our kids that someone might hurt them someday."
"America's Most Wanted" featured Dugard's case three times -- even though many people had given up hope of her ever being found.
When Dugard, now 29, was found living in the backyard of her alleged abductor, Phillip Garrido, Walsh couldn't believe that the 58-year-old had been able to evade authorities time and time again.