In the #1 New York Times bestseller Mindhunter, John Douglas, who headed the FBI's elite Investigative Support Unit, told the story of his brilliant and terrifying career tracking down some of the most heinous criminals in history. Now, in Journey into Darkness, Douglas profiles vicious serial killers, rapists, and child molesters. He is straightforward, blunt, often irreverent, and outspoken, but takes pains not to glorify any of these murderers. Some of the unique cases Douglas discusses include:

-The Clairemont killer
-The schoolgirl murders
-Richmond's First Serial Murderer
-The brutal and sadistic murder of Suzanne Marie Collins
-Polly Klaas' abduction and murder by Richard Allen Davis,
-The tragedy that lead to the creation of Megan's Law

With Journey into Darkness, Douglas provides more than a glimpse into the minds of serial killers; he demonstrates what a powerful weapon behavioral science has become. Profiling criminals helps not only to capture them, but also helps society understand how these predators work and what can be done to prevent them from striking again. Douglas focuses especially on pedophiles and child abductors, fully explaining what drives them, and how to keep children away from them. As he points out, "The best way to protect your children is to know your enemy." He includes eight rules for safety, a list of steps parents can take to prevent child abduction and exploitation, tips on how to detect sexual exploitation, basic rules of safety for children, and a chart, based on age, which details the safety skills children should have to protect themselves.

In his review for Mindhunter in The New York Times Book Review, Dean Koontz said, "Because of his insights and the power of the material, he leaves us shaken, gripped by a quiet grief for the innocent victims and anguished by the human condition." Journey into Darkness continues this perilous trip into the psyche of the serial killer, but also offers a glimmer of hope that profiling may enable law enforcement to see the indicators of a serial killer's mind and intervene before he kills, or kills again.