Edwards was arrested, pleaded guilty to three of the slayings and was sentenced to death. Before he was sent to San Quentin, he made an even more startling admission: He had actually killed 18 children. Detectives began to investigate the claim, but before they could get more information, Edwards hanged himself with a television cord in his cell on death row in 1972.

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FOR THE RECORD:
Serial killer: An article in Saturday's California section about child serial killer Mack Ray Edwards said he hanged himself in prison in 1972. Edwards' suicide occurred in 1971. The article also said the body of victim Dorothy Gale Brown was found by recreational divers off Marina del Rey. Brown's body was discovered off Corona del Mar.

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Thirty-five years later, detectives are taking a new look at Edwards, reopening four missing-child cases from nearly half a century ago that they believe are tied to him.

In the last six months, police have uncovered a letter Edwards wrote seemingly confessing to the killing of a Redondo Beach boy, and have used ground-penetrating radar to check for bodies buried at his former home in Sylmar. They plan to send corpse-sniffing dogs to a half-mile stretch of a Thousand Oaks freeway looking for the remains of another possible victim.

The case has plunged detectives from the LAPD, Pasadena and Torrance police, state Department of Justice and Los Angeles County Sheriff's Department into the yellowing case files of another era. They are trying to track the movements of a serial killer who died more than 30 years ago, reopening the old wounds of families who lost loved ones.

Police say their interest was sparked by the efforts of Pasadena author Weston DeWalt, who was researching the 1957 disappearance of 8-year-old Tommy Bowman in the Arroyo Seco.

While DeWalt was searching old newspapers, a photograph caught his attention. The black-and-white image, circa 1970, showed Edwards in handcuffs as he was led into court.

"I looked at it and I thought: This face looks familiar, but why?" DeWalt recalled. "I studied it for about five minutes and was struck by the resemblance to a sketch I had seen in a Pasadena Police Department file."

That sketch was of a man seen following Tommy before the sandy-haired Redondo Beach second-grader vanished at the head of an Arroyo Seco trail.

DeWalt, the coauthor of a bestselling book about a climbing tragedy on Mt. Everest, came across Bowman's disappearance while researching hiking trails in the Arroyo Seco. He became fascinated by the case and eventually met with the boy's father and detectives, who gave him access to old police records.

"His work has allowed us to go back in time and open up a lot of windows," said Det. Vivian Flores of the LAPD's cold case unit. "There's a lot of families who do not know what happened to their children."

With DeWalt's help, investigators have the first solid evidence that directly connects Edwards to the disappearance of the Bowman boy.

After a 2006 interview with Edwards' widow and other relatives, a family member showed DeWalt a letter from Edwards to his wife, Mary, when he was on death row.

"I was going to add one more to the first statement" to the LAPD "and that was the Tommy Bowman boy that disappeared in Pasadena," he wrote. "But I felt I would really make a mess of that one so I left him out of it."

Last fall, the LAPD obtained a search warrant and confiscated the letter as well as photos and other items from his widow's home.

The break revived painful memories -- but also offered new hope -- for the boy's father, Eldon Bowman, now in his 80s.

Bowman recalled Friday how the family drove up from Redondo Beach to Pasadena for a hike and dinner that March day in 1957. After Tommy vanished, the father refused to go home, searching the canyon and hillside.