Robert J. Sawyer has proven himself to be "a writer of boundless confidence and bold scientific extrapolation" (The New York Times). Now, the Hugo and Nebula Award-winning author explores the thin line between good and evil that every human being is capable of crossing... Experimental psychologist Jim Marchuk has developed a flawless technique for identifying the previously undetected psychopaths lurking everywhere in society.But while being cross-examined about his breakthrough in court, Jim is shocked to discover that he has lost his memories of six months of his life from twenty years previously--a dark time during which he himself committed heinous acts. Jim is reunited with Kayla Huron, his forgotten girlfriend from his lost period and now a quantum physicist who has made a stunning discovery about the nature of human consciousness. As a rising tide of violence and hate sweeps across the globe, the psychologist and the physicist combine forces in a race against time to see if they can do the impossible--change human nature--before the entire world descends into darkness.