In a fit of criminal madness, a married, affluent and respected town-citizen named Gregoire Duval kills a young woman who spurns his advances. As no one witnesses him committing this crime, he chooses to remain silent while the girl's boyfriend, a young Algerian farm worker, is wrongly convicted. In a strange twist of fate, the killer becomes one of the jurors of the trial and suddenly does everything in his power to defend the wrongly accused young man.