Elmer Wayne Henley, Jr. was only fourteen when he first became entangled with serial rapist and murderer Dean Corll in 1971. Fellow Houston, Texas, teenager David Brooks had already been ensnared by the charming older man, bribed with cash to help lure boys to Corll's home. Corll baited Henley with the same deal he'd given Brooks: $200 for each boy they could bring him.

Henley didn't understand the full extent of what he had signed up for at first. But once he started, Corll convinced him that he had crossed the line of no return and had to not only procure boys but help kill them and dispose of the bodies, as well. When Henley first took a life, he felt doomed. By the time he was seventeen, he'd helped with multiple murders and believed he'd be killed, too. But on August 8, 1973, he picked up a gun and shot Corll. When he turned himself in, Henley showed police where he and Brooks had buried Corll's victims in mass graves.

The Serial Killer's Apprentice tells the story of Corll and his accomplices in its fullest form to date. It also explores the concept of "mur-dar" (the predator's instinct for exploitable kids), current neuroscience about adolescent brain vulnerabilities, the role of compartmentalization, the dynamic of a murder apprenticeship, and how tales like Henley's can aid with early intervention.