With Melvil Poupaud as Gaspard, a mathematics graduate and musician, the film opens on a sunlit summer by the sea in Dinard, where he arrives alone and spends his days in a friend's empty flat, composing music and wandering the town. At a local restaurant he meets Amanda Langlet as Margot, a cheerful waitress, and the two quickly form a quiet, easy rhythm of daily walks and conversations about life on the Breton shore. Margot, who holds a PhD in ethnology, interviews local Bretons in her spare time, while Gaspard carries the weight of an on-again/off-again relationship with Léna, Aurelia Nolin as Léna, who plans to visit Dinard. Margot explains that she has a long-distance boyfriend, and Gaspard reflects on his own tangled feelings for Léna as Margot offers calm, candid guidance. Gaspard's clumsy kiss attempt on Margot is gently brushed off, revealing the tension between attraction and hesitation. Margot then takes him on a research trip to a local fisherman's house to discuss maritime folk songs, and the fisherman's stories inspire Gaspard to write his own sea shanty, a shift away from his blues style. He later joins Margot's friends for a night of dancing at a local bar, where he feels out of place until he is acknowledged by Solène, Gwenaëlle Simon as Solène, a sensual, confident, and straightforward former choir singer. She invites him to go sailing on her uncle's boat, and he shares the sea-shanty he has written, while Solène's own romantic stance—she has just broken up with two suitors—frames their budding relationship as a test of timing and commitment. They decide to take a trip to Ouessant, an island off Brittany, the following week. By chance, Léna finds Gaspard on the beach and seems genuinely excited to see him again, rekindling his interest and making him question the vacation with Solène. Back in conversation with Margot, he contemplates whether his actions are clever manipulation or mere weakness, and Margot's steady presence deepens the dilemma. The tension grows as Gaspard secretly plans to be with all three women, a double-booking that he hopes to manage. Then Léna departs in a moody outburst, confessing she is not in love, and Gaspard, walking with Margot, shares a kiss with her again, this time with mutual tenderness. Realizing the stakes, he tells Margot he wants to travel to Ouessant with her, recognizing a bond that feels more honest and caring. Meanwhile, Léna calls to rejoin Ouessant, and Solène also calls to confirm the trip, leaving Gaspard juggling three commitments in the air. A friend then offers a tempting chance to purchase recording equipment in La Rochelle, tempting him to slip away. He explains the situation to Margot at the ferry, and she reveals her own boyfriend's imminent return, tilting the plan toward Ouessant for now; they agree to meet again, though the moment remains unresolved. As the boat pulls away, the old sea-shanty Santiano rises on the soundtrack, leaving a bittersweet sense of possibility and the sense that summer promises more questions than answers.
