The art of the law enforcement interrogation has been diminished over the past several years. In media reports, the noun is usually accompanied by adjectives like botched, brutal, forced or enhanced.

The Last Stone, Mark Bowden's account of the interrogation of a suspect in a nearly 40-year-old missing persons case, goes some way to rehabilitating the questioner's craft.

In March 1975, sisters Katherine and Sheila Lyon, aged 10 and 12, disappeared from a shopping mall outside Washington, D.C. Bowden was a cub reporter at a Baltimore newspaper at the time, and The Last Stone starts by recalling the frantic, fruitless search for the two girls. The case was shelved, but while it faded from the newspapers, it never left the imaginations of detectives in Montgomery County, Md. One after another, they took on the cold case, trawling the same evidence and statements, until one day, in 2013, one of them spotted something that his predecessors had missed.

The discovery led the police to a man named Lloyd Welch, who was serving time for child molestation in nearby Delaware. Welch had come forward during the original investigation and given a statement to the police, but as soon as the cold-case detectives began to speak to him, they realized he had more to say.

A great deal more. Welch talked like "a burst dam," Bowden notes. It was a torrent of information. But it was clear from the outset that most of it was lies. Welch contradicted his original statement, and then went on to contradict himself again, compulsively, layering one half-truth on top of another, changing names and dates and locations with a reptilian smoothness that made it nearly impossible to pin him down.

Had Welch kept his mouth shut, the detectives would probably have moved on. But the more he talked, tying and untying himself, the more interested the team became. Welch knew what had happened to Katherine and Sheila Lyon, they were sure; he may have even been responsible. So they made the drive down to Delaware again and again, conducting a marathon of an interrogation over more than 18 months.

"The path to the truth, or as close as they were likely to get it, was down a long trail of lies," Bowden writes. And not just the lies told by Welch and the living members of his sprawling Appalachian clan. The detectives had to lie constantly: they pretended to empathize with his predicament; they played along when he minimized his stomach-turning offenses; they nodded and appeared to agree when he aired his noxious views. They flattered and praised him continually. They made out they were his best friends.

The stress of the constant lying consumed them. It damaged their lives and their relationships. It affected their work. They made mistakes, some potentially catastrophic. They were not experienced homicide detectives, but they honed their interrogation skills as they went, swallowing their distaste and shrugging off their setbacks as they mined the seams of Lloyd Welch's history. The 18 months they spent facing Welch across a table in an interrogation room in a Delaware prison was as much about stamina and scrupulous attention to detail as it was about exercising the techniques of divining the truth.

The Last Stone is a rigorous documenting of the 40-year journey taken by Montgomery County detectives and the cold-case team that interrogated Lloyd Welch. It's a riveting, serpentine story about the dogged pursuit of the truth, regardless of the outcome or the cost. And it's a useful reminder that in an age of science, forensics, and video and data surveillance, the ability of one human being to coax the truth from another remains the cornerstone of a successful investigation.

Paddy Hirsch is a supervising editor for NPR's Planet Money. You can follow him on Twitter @paddyhirsch.

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