When the promiscuous concierge of a Paris apartment block is murdered, it seems that half the residents of her building had a motive and opportunity to kill her. Inspector Brénot is stumped, so he asks a female friend who lives in the building to make discrete enquiries on his behalf. He doesn't realise how dangerous the assignment is about to become...
Though "Minuit... Quai de Bercy" is written like a whodunit, it doesn't play the whodunit game altogether fairly, withholding vital information we need to deduce the culprit until the last few minutes. The movie proceeds by throwing up one prime suspect after another, each with a secret to hide that may or may not be related to the murder.
The most entertaining of these is Erich von Stroheim, doing a star turn as a religious zealot who hangs around strip joints - in order to distribute pamphlets about Jesus, you understand. He was 67, and looks old and tired, though his tirade at the strip club patrons is the highlight of the movie. There are some decent performances among the other residents/suspects, though few of these characters are fleshed out adequately by the script. As Inspector Brénot, the flabbily nondescript Georges Randax made me long for him to hand the case over to Jean Gabin, perhaps, or Paul Meurisse. It would have made the flirtatious scenes with Madeleine Robinson, as the amateur snoop, easier to stomach.
This is not the worst example of its genre, by a long way, and I found myself watching to the end out of curiosity (and fascinated by Stroheim, who spends most of the last act shouting "Jo!"). For more entertaining and ingenious French whodunits, try Georges Lacombe's "Le Dernier des six" and Clouzot's "L'Assassin habite... au 21".