In Melville's masterpiece, Jef Costello (Alain Delon), aka the Samurai, is a hitman. As he leaves the office where the corpse of Martey, his latest target, was laying, he bumped into Valérie, the club's pianist. Although he has a good alibi, the superintendent suspects him of the murder. When questioned, Valérie pretends not to recognise him. After his release, Jef tries to understand who hired him and then tried to have him killed, and why the young woman did not denounce him...