Coming from a not-well-paid job, a man participates with 25 other candidates in a prison-simulation experiment for two weeks for quick cash as advertised in a newspaper. A makeshift prison is set up in a research lab, complete with cells, bars and surveillance cameras. The candidates are randomly selected to be either prisoner or guard. The experiment begins smoothly, but quickly deteriorates as the guards develop megalomaniac tendencies. Soon, quarrels arise and the wardens employ ever more drastic sanctions to confirm their authority.