In a moment of madness a middle-aged, married and respectable pharmacist kills a young woman who is sun-bathing by a lake. Unable to take in what he has done, he flees from the scene of the crime and behaves as if nothing has happened. Eventually her boyfriend is charged with the crime and, in a strange twist of fate, the killer finds himself serving on the jury.
A group of ex-resistance fighters are brought together by Marie-Octobre, the code name of Marie-Helene Dumoulin. The former members of the network have carried on with their lives after the war, but this evening they are going to have to live again a fateful night – the night their leader was killed. He had been betrayed, his name given to the Germans. The search for the traitor puts each personality in the spotlight – and also that of the killed leader, Castille.
The Marquis de Villemaur reunite strange visitors in his Castle, to meet a survivor of the Third Reich. There is an Italian fascist, Heinrich; a German, Matthias; a Russian; and Dromard, a blind French war hero with a black monocle.
Vallois, a vice inspector for the Paris police, takes special interest in the plight of drug-addicted Lucky (Najda Tiller), whom he considers to be more victim than criminal. Taking it upon himself to wean Lucky away from narcotics, Vallois also wins her love -- and, incidentally, smashes the dope ring responsible for her addiction.
Agathe Perrin, a wealthy widow in her forties, lives with her ailing father in an estate on the shores of Lac du Bourget, not far from Aix-les-Bains. For the past four years, she has been involved in an affair with a twenty-four-year-old artist, Jackie, that is beginning to weigh heavily on her. The frequent visits of a brilliant Aix doctor to the sick old man's bedside have distracted Agathe from her very young lover. She'd like to send him away, but he clings to her desperately, and we witness the drama of this break-up, both feared and rejected by Agathe. Blinded by jealousy, Jackie decides to leave, but not without behaving like a spoiled, insolent child.
In 1943, a German commando conceals a large quantity of gold in an undersea cave on the coast of Corsica. Years later, Schlumpf, the sole survivor of the commando, returns to Corsica to recuperate the treasure -- with British and Soviet spies on his heels, and closely monitored by Dromard, from the French intelligence services. The monocled Dromard is convinced that he can outfox his opponents, but difficulties accumulate: despite his plump appearance, Herr Schlumpf is a sly fellow; Corsica is teeming with treasure hunters from various nationalities; and all parties readily resort to unnatural alliances, brazen treachery, and strong-arm tactics. Who will get the treasure?
An art dealer in dire straits, after being ripped off by two crooks, one of whom owns a genuine painting by Gauguin while the other is an expert copyist, finds them again and, instead of killing them as he originally intended, joins in their game – with ultimately disastrous results.
