This film is adapted from a true story. The story takes place at Stanford University in the early 1970s, where a group of college students conducted a research experiment on human behavior. They were divided into two groups, one group played the role of prison guards, and the other group played the role of prisoners. They began to simulate the daily life in prison for 24 hours. It turned out that the people who played the prison guards began to become violent in the simulated prison situation, while the people who played the prisoners planned to rebel. The experiment was stopped soon, but its research results have been concerned by people for many years and caused widespread controversy.