It all begins and ends with The Argument: Free will is an illusion. The soul? Merely neurons firing.

Someone is determined to prove the truth of The Argument, no matter who has to die.

Psychology professor Tom Bible is surprised to find the FBI on his doorstep, asking for help analyzing the prime suspect in a series of gruesome murders.  That’s not what Tom does—he’s just a teacher, not a profiler.  But in this case, the FBI feels Tom has special knowledge. 

The suspect is his best friend Neil Cassidy.

Using the neuroscience he developed at the NSA, Neil can control the human brain. With just the flip of a switch, he can manipulate pain, pleasure, faith, morality....even love. He taunts the FBI with videos, forcing them to watch as his victims destroy themselves at the direction of their captor. He leaves no clues and the FBI cannot predict his next victim. Only Tom Bible has insight into his mind.