Les Cousins (1959) was directed by Claude Chabrol and belongs to the French New Wave movement which emerged in the 50s. I enjoyed it for its twirling camera shots and oblique angles and Fellini-like party scenes. It must've pushed the limits in terms of how much lewdness and debauchery could be shown on screen at the time. Quite a few characters are introduced, some essential to the plot, others for decoration, but more than is typical for a 50s film. This is Stéphane Audran's first major appearance and although she plays a small role, she stands out for her good looks and her character's sauciness.
The provincial Charles (Gérard Blain) moves in with his cousin, Paul (Jean-Claude Brialy), who has a flat in Paris. Both are law students but with opposite personalities. Paul is decadent and lecherous and neglects his studies outright, whereas Charles the naive mama's boy prefers books over his dissolute new friends. Charles refers to himself as the "plodding" type. Paul sleeps with the woman his cousin has fallen for, Florence (Juliette Mayniel). I read there were two endings planned, one positive which has the cousins reconcile, the other pessimistic and tragic. They chose the latter.