Katherine and Sheila Lyon grew up in Kensington, Maryland, in a close middle-class household on Plyers Mill Road. Their father, John Lyon, was a well-known radio personality at WMAL-AM, a local station affiliated with the ABC network and the now-defunct Washington Star newspaper. The girls were two of four children -- the only daughters, bracketed by an older brother, Jay, and a younger brother, Joseph. On that spring afternoon, the Lyon sisters walked the short distance to Wheaton Plaza, a familiar errand. Eyewitnesses would later recall seeing the girls in conversation with a young man carrying a tape recorder and microphone. He told them he recorded people's voices and put them on the radio. Sheila, the older sister, giggled. Then the girls were gone.

Within days, a man named Lloyd Lee Welch appeared at a police station and gave a six-page statement. He claimed to have witnessed the girls being forced into a red Chevrolet Camaro with white upholstery by a man with a tape recorder. The account briefly electrified investigators and touched off a frenzy of citizen band radio users scouring the area for a matching vehicle. But when Welch failed a polygraph test, he admitted he had provided false information. Police lectured him about lying and let him go. His statement was filed away. No matching vehicle was ever found. The case gradually went cold. By summer 1975, the Lyon family had resigned themselves to the likelihood that their daughters were dead. The bodies of Katherine and Sheila Lyon have never been found.

For decades, the Lyon sisters' disappearance received periodic reviews but yielded no breakthroughs. Investigators explored other suspects, including a convicted sex offender named Fred Coffey who had been in Montgomery County the week after the girls vanished and was known to lure children using devices like metal detectors and fishing rods. But Coffey was younger than the man witnesses described, and authorities could not place him at Wheaton Plaza on March 25. By 2013, most of the original investigators had retired or died. A decision was made to review the archived case from scratch. Sergeant Chris Homrock, examining every preserved record, returned to Welch's original six-page statement -- and noticed something critical.

Homrock compared a 1977 mug shot of Welch, taken for an unrelated burglary, with the 1975 composite sketch of a young man witnesses said had been leering at the Lyon sisters inside Wheaton Plaza shortly before they vanished. The resemblance was striking. By this time, Welch had compiled an extensive criminal history between 1973 and 1997 -- rape, domestic violence, assault with a knife -- and was nearing the end of a twenty-nine-year sentence for child molestation. Investigators began interviewing Welch. Across twelve subsequent sessions, his story shifted constantly: he denied involvement, then implicated relatives, then admitted to planning the kidnapping while insisting he had not participated in the murders. But with each contradiction, he inadvertently revealed details that only a direct participant could have known. In September 2017, Lloyd Lee Welch pleaded guilty to the murders of Katherine and Sheila Lyon and was sentenced to forty-eight years in prison. The case -- one of the most notorious unsolved crimes in Washington-area history -- had taken forty-two years to close.