Jean-Paul, a writer, portrayed by [Alain Delon], and Marianne, his girlfriend of just over two years, played by [Romy Schneider], are holidaying at a friend's villa near Saint-Tropez. The poolside opening tone is tense and intimate: Marianne asks for a back scratch, he obliges, then unexpectedly shoves her into the water and dives in after her. A later moment grows more unsettling as he uses a branch to lash her bare buttocks—playful at first, but the force of it thickens as the scene cuts away, hinting at a volatile undercurrent beneath their flirtatious surface.
Harry, an old friend and record producer who was Marianne's lover before Jean-Paul, arrives with his 18-year-old daughter Penelope, played by [Jane Birkin]. They arrive unannounced, and Marianne invites them to stay, much to Jean-Paul’s surprise. The four stay together, and Harry’s presence stirs old tensions as he rekindles his pull on Marianne. Harry drinks heavily and throws a surprise party while Jean-Paul, a recovering alcoholic, makes a valiant effort to stay sober. Penelope, whom they had not known about, resists her father’s authority and forms an uneasy bond with Jean-Paul, with whom she spends a day along the sea, testing loyalties and boundaries.
As days pass, the house becomes a pressure cooker of desire, pride, and hidden grievances. Harry’s charisma and drinking deepen Marianne’s pull back toward him, while Penelope’s wary independence draws her closer to Jean-Paul. The dynamic between the two men sharpens, and Penelope’s presence magnifies the unspoken competition simmering beneath the surface of their holiday idyll. The atmosphere grows increasingly charged, and the line between play and peril blurs in the bright light of the coast.
One night, after the women are asleep, Harry confronts Jean-Paul in a drunken flare-up and accuses him of seducing Penelope to lash out at his own failed ambitions. A brutal moment follows: Harry falls into the pool and, unable to swim, slips from the surface as a struggle ensues. Jean-Paul, also drinking, initially resists helping him, then deliberately holds him underwater until he drowns. He discards Harry’s clothes and arranges fresh ones by the pool to make the death look accidental, a cover-up that haunts the remainder of their time at the villa.
After the funeral, Inspector Lévêque visits and questions the family, doubting the accident theory. He notes unambiguous inconsistencies—Harry’s expensive watch, not waterproof, is missing, and there is no sweat on the clothes he was supposed to have worn. Marianne, torn between truth and loyalty, learns of the evidence but does not hand it to the police, and the inquiry is reluctantly suspended. Marianne later takes Penelope to the airport, and Penelope presses for the truth; Marianne insists that Harry’s death was an accident. As they prepare to leave, Marianne calls for a taxi but Jean-Paul intercepts the call, freezing the moment and forcing a silent standstill. In the final shot, they stand side by side at the window, looking out at the pool, and then embrace, leaving the moral question unresolved and the future uncertain.
