In this first-person account of becoming the FBI's top serial-killer hunter and a member of a religious order in an attempt to discern the true nature of good and evil, Roger L. Depue searches for an understanding of how evil develops. Between Good and Evil is Depue's look back at a life spent apprehending criminals, especially serial killers, first as a small-town police chief, then an FBI-SWAT team member, Behavioral Sciences Unit chief, and a developer of revolutionary law enforcement programs.

The book also examines Depue's experience studying with the Brothers of the Missionaries of the Holy Apostles in an attempt to discover why a good person like his wife, whom he had lost to cancer, is allowed to die while monstrous criminals get to live. Following his time in the clergy, Depue returned to law-enforcement and today heads one of the world's most elite forensics think tanks, "The Academy".