Card-carrying members of the Cult of Jean-Pierre Melville claim that this 1962 tale about double crosses and dirty rats is the filmmaker’s first true policier. That’s close, but no Gauloise; despite an interrogation scene captured by a virtuosic eight-minute single shot, this thriller isn’t a precinct opera but a hard-boiled primer for criminals on their own internal-affairs beat. Few films have focused so intently on proper underworld etiquette: You must wear overcoats, sport cocked fedoras and have a cigarette dangling from your lips at all times. Keep the fuzz chasing their own tails. And though the title is thug slang for an informer, you never, ever sell out a fellow thief unless you’re prepared to pay the price.

Trying to keep up with the movie’s metapulp narrative of colliding ironic reversals of fate can leave you punch-drunk. But tracking who’s possibly screwing whom is only part of the game; as with Melville’s Le Samourai (1967), the atmosphere of low-life chic means just as much as plot mechanics. Everybody from cinematographer Nicolas Hayer, whose shadowscapes rival noir master John Alton’s best work, to actor Serge Reggiani (imagine a rumpled Rowan Atkinson) contributes greatly, but the second Jean-Paul Belmondo’s Easter Island mug fills the screen, there’s no doubt who owns Le Doulos. Alain Delon may have been Melville’s stoic, sexy angel of death, but the Breathless star plays subzero cool with such panache that, in a perfect world, cinephiles would perpetually run their thumbs across their bottom lips and utter his name instead of Bogie’s.