The Collector (E. Rohmer, 1967)

Two friends, Daniel and Adrien, are invited to vacation at a mutual friend’s house by the sea in Saint-Tropez while Rodolphe is away. When they arrive they discover another friend of Rodolphe’s is also staying there, a very young woman named Haydée who turns up, often very late at night, with a different lover each time they see her. The solitary vacation each of the friends had envisioned for themselves is dashed on the rocks of Haydée whom they first resist but then can’t resist and it’s not clear who is really in control of this game of “collecting” relationships.

(Source : en.wikipedia.org)