Pierre enjoys a carefree existence with his widowed mother in a beautiful chateau in Normandy, relishing his growing fame as an anonymous author. He frequently visits his childhood friend and fiancée, Lucie, at her family's chateau. One evening in a bar, he encounters his cousin Thibault, a stockbroker, who offers Pierre a place to stay in Paris. However, he can't help but wonder about the young vagrant woman who has been following Pierre. When Pierre looks back, the mysterious woman hastily flees.
While driving through the forest, Pierre is unsettled to see the same vagrant, who resembles a ghostly figure from his dreams. She approaches him with a distinctive foreign accent, introducing herself as his half-sister, Isabelle. Isabelle shares her tragic story, revealing that she and her companions—a Romanian woman named Razerka and a small girl—are refugees fleeing the turmoil in Eastern Europe.
In a drastic change of heart, Pierre abandons his home, mother, and fiancée, taking Isabelle to Paris. He hopes to stay with Thibault, but Thibault coldly refuses to acknowledge him and dismisses them from his apartment. Navigating the unfamiliar streets of Paris and fearing deportation, the group finds a budget hotel to stay in. Inspired by his new surroundings, Pierre decides to set aside his initial ideas for a second novel in favor of a dark, more mature narrative that reflects the harsh realities of life. However, his publisher cautions him that this new direction may lead to insincerity and inferior writing, refusing to grant him an advance.
At the zoo, Pierre, harboring a deep cynicism, coldly tells the small girl that the animals are unhappy because all humans stink. The girl innocently spreads this telling truth on the streets, but soon faces a brutal retaliation when she is slapped by a stranger, leading to a tragic incident that results in her untimely demise. Once again feeling the weight of potential deportation, Pierre, Isabelle, and Razerka move a corpse to a dilapidated warehouse controlled by a terroristic cult. In exchange for escorting Razerka safely to a known contact, the trio receives shelter. The group, dedicated to guerrilla warfare and industrial music, fosters an environment where Pierre and Isabelle’s incestuous passion takes shape as they bond over their shared trauma.
Amidst this chaos, Pierre remains fixated on his writing, even as he learns of his mother's tragic suicide. During a bleak winter, Lucie finds Pierre at the warehouse, exclaiming her desire to reside there under a pseudonym to 'shield' Isabelle from the reality of Pierre’s abandonment. Accepting the new dynamics of their relationship out of unwavering love, both Pierre and Lucie keep their true feelings hidden from one another. Meanwhile, Isabelle feels lost and inadequate, striving to ingratiate herself with Lucie and even asking to care for her during her frequent bouts of illness.
In desperate need of funds, Pierre appears on television to unveil his identity, only to be met with skepticism and hostility from an audience disconnected from his earlier literary success. As he continues to write through the winter, Pierre dreams of himself and Isabelle engaging in a passionate yet horrifying encounter, culminating in their drowning in a river of blood. One day, while walking along the Seine, they come across an autobiography of Pierre's father. He is unsettled to discover that Isabelle does not recognize the man depicted on the cover, claiming to have met him just once. Doubt seeps into Pierre's mind, triggering an existential crisis in Isabelle, which leads to an attempted suicide and a subsequent hospital visit where a vengeful Thibault unveils Lucie’s true identity to her.
Facing yet another blow to his aspirations, Pierre is met with a harsh rejection from his publisher after submitting his work anonymously. Isabelle confronts Pierre about his deceit, while Pierre feels heartbroken witnessing Lucie degrading herself by living in a squat, watching his every plan crumble. After receiving an invitation from Thibault to engage in a confrontation, Pierre steals firearms from the cult and decides to seek out Thibault in central Paris, where he makes a fateful decision to shoot Thibault in the head, leading to his immediate arrest. Overcome with despair for losing Pierre, Isabelle insists that she has never lied to him, tragically throwing herself in front of a vehicle as he is taken away to jail.
