Jacques Darnay (Delon) is released after having served ten years in prison for robbing a jewelry store. Much about that crime remained a mystery: the stolen diamonds were never recovered, and no one knows exactly how Charby the jeweler died. At his trial it was declared that Darnay acted alone, yet the size and complexity of the heist make that seem highly unlikely. Darnay's release is anxiously awaited, by both the police, who hope he'll reveal more information about the crime, and by some of Darnay's former friends, who have a few ideas as to what might have happened to the diamonds. Having, perhaps, played in his years enough of both, Delon is the perfect point man in this duel between cops and crooks, capitalizing on each side's strengths and weaknesses while decidedly pursuing his own agenda.