Gaspard, a recent graduate in mathematics and a budding musician, spends his summer vacation by the serene seaside town of Dinard. Alone in his friend's vacated flat, he indulges in composing music and wandering through the picturesque streets. During his visits to a local restaurant, he crosses paths with Margot, a vibrant waitress with a zest for life. Although Gaspard is hesitant at first, a warm friendship blossoms between them, leading to daily strolls through the charming locale.
Margot, who possesses a PhD in ethnology, is busy conducting research interviews with local Bretons. Gaspard, meanwhile, finds himself in a complicated relationship with his on-and-off girlfriend, Léna, who is planning a visit to Dinard. Margot, too, reveals that she has a long-distance boyfriend. As Gaspard shares the trials of his entangled romantic life, Margot offers him sage advice. In a clumsy yet endearing moment, he attempts to kiss her, only to have Margot gently deflect his advances.
Their friendship deepens when Margot takes Gaspard on a research expedition to a fisherman’s home to explore maritime folk songs. Inspired by the tales he hears, Gaspard crafts his own sea shanty, marking a departure from his usual blues style.
Later, Gaspard joins Margot and her friends for a lively evening of dancing at a local bar, where he feels somewhat out of place. The next day, he encounters Solène, one of Margot's friends who exudes confidence and sensuality. She invites Gaspard for a sailing adventure on her uncle's boat, showing a keen interest in his music. As he teaches her the sea shanty he composed, Gaspard's spirits lift, bolstered by her attention. Just as Solène is recovering from her own breakup, Gaspard, recognizing her as a viable romantic interest, agrees to a trip to Ouessant, an island off Brittany's coast.
Unexpectedly, Léna finds Gaspard at the beach, radiating excitement at their reunion. This newfound warmth confounds Gaspard, who begins reconsidering his plans with Solène. He confides in Margot about his growing conflict, while she becomes entangled in his emotional turbulence. Margot raises questions about Gaspard's tendency to float between relationships, pondering whether he is manipulative or simply indecisive. Ultimately, Gaspard ensnares himself in a double-booking dilemma, promising trips to both Léna and Solène.
After a turbulent confrontation, Léna admits she is not in love with him, leaving Gaspard to contemplate Solène as his only option. Yet, during another outing with Margot, they share a kiss that sparks new feelings between them. Frustrated with Léna's fickle nature and Solène's expectations, Gaspard resolves to travel to Ouessant with Margot, realizing that their relationship feels more genuine and nurturing.
As Gaspard tries to untangle his commitments, both Léna and Solène reach out to him, complicating matters further with their respective intentions to join him on the trip. Just when things seem overwhelming, a friend presents him with an opportunity: recording equipment available for sale in Rennes. Seizing this chance, Gaspard decides to leave town, evading his romantic entanglements.
Before his departure, Gaspard meets Margot at the ferry to Saint Malo to share the developments. Margot reveals that her boyfriend is returning soon, and she intends to visit Ouessant as well. This news takes Gaspard by surprise, as he had assumed Margot's unwavering presence in his life. They make ambiguous plans to see each other again in the future, sharing a passionate farewell kiss as they descend the ramp towards the boat. As the vessel sets sail, Margot waves goodbye, and Gaspard's old sea-singing shanty, "Santiano," resonates in the background, echoing the unresolved emotions between them.
