A young girl burns down the family home A man doesn't remember killing his wife A teenager's visions and voices lead to murder One question binds these and many others from the casebook of Britain's leading forensic psychiatrist: Why? What drives a person to commit seemingly inexplicable crimes? Dr Duncan Harding is the person the police and the courts turn to for answers - to establish a defendant's mental state and motivation: their fitness to stand trial. It is a career that has brought him face to face with psychopaths, taken him to the limits of human compassion and to the darkest corners of his own troubled past. This then is a journey deep into the criminal mind . . .