Jacques Darnay is arrested and wrongly convicted for a diamond heist in which a jeweler died. Darnay serves eight years in jail. On his release, he is kept under close scrutiny by police chief Rouxel and by the criminal underworld. No one has ever found the diamonds. Ex-gangster Gino Ruggeri offers Darnay his protection and loans him money, accommodation and his mistress, Nathalie. In fact, Ruggeri, is the leader of the gang which killed off Darnay's best friend and now intends to eliminate him. With Nathalie's help, Darnay gets to Ruggeri first and heads off for South America where the diamonds are hidden.