Intertitles at the beginning of the film explain that the French title refers both to a kind of hat and to the slang term for a police informant.

[3] Maurice Faugel, just released from prison after serving a six-year sentence, meets a friend, Gilbert, who is appraising the value of jewels from a recent heist.

Meanwhile, Silien comes to Thérèse's apartment, then beats her and ties her to a wall radiator, demanding to know the address of the robbery.

He leaves Anita with a diagram showing where he buried the jewels, money, and gun, telling her to give it to Jean if something happens to him.

Silien stumbles over to the phone and tells Fabienne he will not see her that evening before adjusting his hat in a mirror and falling down dead.

Le Doulos was shot at Melville's rue Jenner studios in Paris between April and June 1962.

[2] The French Censorship Commission classified it as forbidden to minors below the age of 13 "in view of violent content which may shock children",[2] and this classification stood until 1983, when the film was passed for all audiences.

[5] The film received strong reviews in France, with Melville biographer Ginette Vincendeau stating: "References to masterly technique, sobriety, elliptical style and narrative efficiency graced almost every review, summed up by L'Express as 'quasi perfection of Le Doulos.

'"[6] Claude Beylie wrote in the influential Cahiers du Cinéma that Le Doulos possessed "moral reflection" on truth and lies, and demonstrated an "extraordinary craftsman’s precision, a high love of style."

Contemporary American indifference to Melville’s work was typified by a 1964 review in The New York Times, which called the film tiresome, excessively talkative, and cluttered with confusing references to irrelevant events.

The reviewer considered the movie pseudointellectual and superficial, saying: [T]here's not much to recommend the picture, which is one of those feeble attempts to be philosophical and mordant about crime as a chosen career.

[7]On Empire magazine's 2008 list of the 500 Greatest Movies of All Time, Le Doulos was ranked number 472.

[9] American filmmaker Quentin Tarantino cited the screenplay for Le Doulos as his personal favorite and a large influence on his debut picture Reservoir Dogs.