Unemployed Travis (Adrien Brody) enrolls in a psychological role-playing experiment, where participants assume the identities of inmates and prison guards in an empty jail, with the promise of a $1,000-a-day reward. Another participant, Barris (Forest Whitaker), embraces his correctional officer role with a vengeance, and before long, the prisoners find themselves at the mercy of their keepers. All the test subjects discover how easily violence and cruelty can manifest itself in human behavior.