Are psychopaths 'evil' and untreatable, or do they suffer from a form of mental illness comparable to schizophrenia? Do they have free will? Do we? In this at once terrifying and exhilarating account, neuroscientist Kent Kiehl guides us through the dark world of a psychopath's mind, a disconnected place where emotion is dead and guilt is absent. Drawing on groundbreaking research, including personality surveys and brain imaging scans of thousands of criminals, Kiehl pinpoints the biological machinery of psychopathy and offers a radical new perspective on identifying and treating the psychopaths in our midst.