Tomas, a talented German filmmaker residing in Paris, has just wrapped up his latest cinematic endeavor. At the jubilant wrap party, he encounters Agathe, a spirited young primary school teacher. The atmosphere is electric as Tomas, with a twinkle in his eye, asks Agathe to dance after her husband, Martin, an English printer, turns down the offer. The pair soon find themselves at Agathe's home for an after-party, where they share a passionate night together.
Upon returning home the next day, Tomas, who spent the night at Agathe's, confesses to Martin that he has had an intimate encounter with a woman and, for the first time in ages, he experienced feelings that were long buried. This admission stirs unrest as Tomas argues that their marriage is crumbling. Frustrated by Martin's reluctance to engage in a deep conversation about their relationship, he begins packing a suitcase to leave. However, Martin stops him, sharing a tender kiss and offering reassurances that they can work through their troubles.
Later on, Agathe pays a visit to Tomas in the editing room of his film, leading to yet another intimate rendezvous. As their relationship deepens, Tomas and Martin decide to spend some time at their country house—a much-needed getaway where they confront the underlying issues in their relationship. During this heartfelt discussion, Tomas expresses his discontent with their too-comfortable and safe bond. On the other hand, Martin accuses him of falling head over heels for Agathe.
Back in the bustling heart of Paris, Martin crosses paths with Amad, a writer and novelist, through a mutual acquaintance at a restaurant. When Tomas shows up later, he can't hide his contempt for Amad, labeling him "an arrogant prick." Displeased, Tomas, under the pretext of heading to the editing room, sneaks off to spend the night with Agathe instead. The next morning, after a comforting lullaby from Agathe reminiscent of his childhood, Tomas reveals a startling confession—he has indeed fallen for her.
The escalation of events leads to the official separation of Tomas and Martin. Tomas moves in with Agathe, but during the moving process, he stumbles upon a book by Amad that Martin is reading, igniting feelings of resentment. As he prepares to leave, Martin shares the news that he plans to sell the country house, expressing a desire to sever all ties with Tomas.
As Martin begins to date Amad, Tomas unwittingly encounters him when he uses his key to enter Martin's apartment without prior notice, leading to an explosive confrontation that has Tomas storming out in a fit of rage. Things come to a head when Tomas brings the disheartening news to Martin that his film's first screening did not go over well, resulting in Martin asking for the apartment keys back.
While dining with Agathe and friends, Tomas spots Martin entering with his companions, yet the air remains thick with unspoken tension as neither man acknowledges the other. Later on, Tomas decides to return the keys, all the while inviting himself to stay over and join Martin for repairs at the country house the next morning, claiming his stake in the property. That night, desire takes over as Tomas slips into Martin's room, resulting in a passionate encounter, only to drop a bombshell the following morning—Agathe is pregnant.
Tomas arrives late for dinner at Agathe's parents' house, where he faces a barrage of inquiries about his intentions to support Agathe and their impending family. Defensive and tense, he struggles to articulate his plans, particularly concerning his past with Martin. Then, he makes a sudden trip back to Martin's apartment, professing joyful news that the latest screening of his film was a hit. Taking a bold step, he kisses Martin and suggests they raise the baby together. In a tumultuous turn, Martin breaks up with Amad, who ominously warns that neither man will ultimately endure such a chaotic relationship.
Some time later, the group gathers at the serene country house. From another room, Agathe hears the sounds of Tomas and Martin as they become intimate, a poignant reminder of the tumultuous dynamics at play. Eventually, in a moment of intimacy, Tomas joins a tearful Agathe in bed, offering comfort and companionship as they navigate the emotional turmoil together.
In a drastic move, Agathe decides to cut off ties with Tomas and later meets with Martin, where she confides her heartbreaking decision to undergo an abortion. With the weight of her choice hanging heavy in the air, she expresses her desires for a family yet acknowledges that being part of their complex trio would make her feel submerged. Overcome with emotion, Martin holds back tears as they bid farewell.
Upon returning home, the emotional strife culminates as Martin confronts Tomas, ending their relationship and refusing to accompany him on a trip to Venice. He orders Tomas to cease all communication with him. In a final desperate attempt for reconciliation, Tomas visits Agathe at her school, pleading for forgiveness and inviting her on his journey, but she firmly declines. Heartbroken and disoriented, he escapes the confines of his troubling reality, aimlessly cycling through the city, lost in a whirlwind of unfulfilled desires and shattered relationships.
