In this tense, psychological thriller based on the notorious true story, Billy Crudup stars as Stanford University professor Dr. Philip Zimbardo, who, in 1971, cast 24 student volunteers as prisoners and guards in a simulated jail to examine the source of abusive behavior in the prison system. The results astonished the world, as participants went from middle-class undergrads to drunk-with-power sadists and submissive victims in just a few days.