In basement offices three stories below the ground at the FBI's Academy in Quantico, Virginia, former Supervisory Agent Gregg McCrary was among the first generation of the most elite force for criminal investigation in the world. In The Unknown Darkness, McCrary takes the reader behind the crime scene to examine in raw first–person close–up the lethal competition between America's most dangerous predators and the dedicated souls who pledge to put them away. McCrary's 25 years in the Bureau have yielded over 1000 cases to draw upon. The 10 he describes in the book reveal the strengths and pitfalls of modern criminal investigation. McCrary is not afraid to answer the questions most often skirted by the others: what happens at the crime scene, what kind of person does it take to grapple with the serial killers among us, and exactly how do we disarm the enemy?