They are charming, they lie without scruples and are capable of manipulating their environment. Psychopaths murder and rape without remorse and can still come across as disarmingly pleasant. What’s going on in their minds? As can be seen in films, art and literature, evil - seemingly devoid of morals and law - exerts a fascination over us. Centuries ago, anatomists tried to open human skulls and penetrate the brain. Today, state-of-the-art appliances enable us to scan brains to make inner processes visible. In this documentary, experts present their theories, experiments and results: how can decent people become ruthless murderers?