Marseilles, 1919. Georges Sarret is a distinguished and respected lawyer, recently honoured for his services in the First World War. He takes as his lover Philomène Schmidt, a young German woman, who has just lost her job and home. To enable Philomène to remain in France, Georges finds her a husband – who dies conveniently of natural causes a month after the wedding. Georges repeats the trick with Philomène's sister, Catherine – marrying her off to an old man who dies suddenly so that the scheming trio can profit from his life insurance. When an accomplice in the scheme, Marcel Chambon, threatens to blackmail them, Georges and his two lovers have no option but to kill him and his mistress...
Unfortunately the movie The Infernal Trio is not yet available on HBO Max.
| Editing | Claude Barrois | Editor |
| Writing | Francis Girod | Screenplay |
| Production | Raymond Danon | Producer |
| Production | Jacques Dorfmann | Producer |
| Sound | Ennio Morricone | Original Music Composer |
| Camera | Andréas Winding | Director of Photography |
| Directing | Francis Girod | Director |
| Writing | Jacques Rouffio | Screenplay |
| Costume & Make-Up | Jacques Fonteray | Costume Design |
| Writing | Solange Fasquelle | Novel |
| Production | Wolfdieter von Stein | Producer |
| Art | Jean-Jacques Caziot | Production Design |
| Art | Philippe Turlure | Set Decoration |
| Production | Alain Coiffier | Production Manager |
| Production | Ennio Nobili | Co-Producer |
