Aug. 10, 2007 -- The abduction and murder of 6 ½-year-old Adam Walsh, who disappeared in 1981 from a Florida mall, is perhaps one of the most famous cases of child abduction and murder in America.
It was a crime that outraged a nation and propelled Adam's father, John Walsh, to devote his life to fighting crime on the television program "America's Most Wanted."
John Walsh remains convinced the killer of his son was drifter Ottis Toole, and Walsh's longtime friend and colleague Joe Matthews believes he has incontrovertible proof -- although the crime remains officially unsolved.
But in those chaotic early days of the investigation, in a time before amber alerts and DNA, what clues may have been missed?
Now a fascinating new theory has surfaced: Could one of the most famous murders of our time have been the work of one of the most famous murderers of all time?
For the past 11 years, a true-crime author named Arthur Jay Harris has been investigating the case on his own, and he has uncovered a shattering revelation. Who was working only minutes from that mall that morning? Jeffrey Dahmer, the serial killer.
Using public records, the 7,000-page police case file and a lot of legwork, Harris discovered that the same day Adam disappeared, two witnesses independently contacted the police to describe a thin, disheveled blond man who had been acting strangely in the mall.
One witness said he even followed the man to the toy department -- the last place Adam was ever seen. Police don't dispute that these witnesses came forward at the time, although no record of their statements exists.
Flash forward 10 years to July 24, 1991. Jeffrey Dahmer had just been arrested in Wisconsin for murdering 17 people. Six hundred miles apart, both witnesses opened the morning paper, took one look at his photo and said, "That's him."
Both contacted the Hollywood police department to report that the man they had seen 10 years before in that mall was Jeffrey Dahmer.
In 1992, Florida police actually went to interview Dahmer, who denied killing Adam Walsh. But a former FBI agent now said that Dahmer later privately hinted he had committed the crime.
Just three months ago, "Primetime" was there as Harris made a key discovery: an official report lost in plain sight for 26 years… a discovery that led our cameras to a long-forgotten room.
In a dark back alley of a Florida mall there is an ordinary door. But behind that door, did something dreadful happen 26 years ago? And could it hold a tantalizing clue to a crime that's haunted America for decades?
Find out on "Primetime: Crime" Tuesday at 9 p.m. EDT.