What makes a normal person a serial killer? Why do some people like to torture others? Do some of us have evil in our genes? These questions have always kept people curious. The approaches to explaining evil are as diverse as evil itself. The latest science assumes that there are three factors that shape human behaviour: genes, the environment, and the situation. All three factors work together and influence each other. The film presents the latest information and findings with one of the most exciting questions in behavioural research.