I actually kept up with all the plot confusion, so better write this down while I still remember it. Thief Maurice (Serge Reggiani, would-be star of Clouzot’s Inferno) kills and robs his fence/friend Gilbert (Rene Lefevre, Monsieur Lange in The Crime of Monsieur Lange), goes home to girlfriend Therese, hangs out with friends Silien and Jean, then gets caught robbing a house the next night, kills a cop who knew Silien and Gilbert, and gets arrested for both killings, neither of which can be proven.
From another POV (with a few holes), as soon as Maurice leaves Therese’s house robbery, buddy Silien (Jean-Paul Belmondo, one of three Melville movies he did between Breathless and Pierrot Le Fou) runs in, ties up Therese (smacking her around first) and asks her where the robbery is taking place. Cops cars arrive just as Maurice’s partner has started drilling the safe – the partner and the cop are killed, and Maurice faints with a bullet wound, picked up by persons unknown in a car. Belmondo visits the police station, a known informer, and offers to call around the bars looking for Maurice – they catch him in one, and he’s arrested. Meanwhile, Therese turns up dead in her car at the bottom of a ravine. Looks like Belmondo has locked up Maurice for offing his cop friend, and killed his girlfriend too. On top of that, Belmondo finds the buried jewels, cash and gun from the Gilbert killing (Maurice had left Therese a map, in case anything happened to him). In jail, Maurice (who’s as much the star of the movie as the over-the-title-credited Belmondo) hires a dude to kill Belmondo once they get out.
But Belmondo turns out to be a true friend who’s extremely good at covering for Maurice’s crimes. Belmondo killed the girl for ratting, saved Maurice at the scene of the heist, met up with his own ex-girl (Fabienne Dali of Kill Baby, Kill) and used the jewels to frame Michel Piccoli for the murder(s). So all is well… or it would be, but Maurice remembers that he’s got a hit man after his friend, so he races to Belmondo’s house and everybody gets killed.
So much twisty plot going on, I barely noticed anything else. Seemed like one of Melville’s more busy, exciting films.