Catherine Girard, Charlotte Gainsbourg is blood-splattered in a police station as she confesses to killing her husband’s first wife earlier that day. She provides what looks like the murder weapon, but Detective Fordham, Mike Tsar, isn’t convinced because the crime took place three years earlier. To prove herself, Catherine begins to recount the events that led to the act, a story that keeps twisting between past and present and leaves room for doubt about what really happened.
Three years earlier, Catherine and Nick Girard, Charles Powell, meet at a gallery. After a mugging injures Catherine, Nick rescues her and invites her to stay with him while she recovers from a twisted ankle. The attraction quickly becomes love, and they marry. Nick—a widower who is reticent about his dead wife Stella—seems generous, but his past casts a shadow over their happiness. Their circle of friends—Badge Mueller, Nastassja Kinski a sharp art broker who lives in the loft below, Charlie, John Hannah a mathematician and video game programmer, and Daisy, Molly Parker Charlie’s on-and-off girlfriend—helps paint a picture of a life they’re building together. Catherine learns that Stella was murdered three years ago after an apparent struggle, and she discovers that Stella’s mental state had strained Nick’s marriage to the breaking point.
As the days unfold, Catherine grows paranoid that someone has been sneaking into their apartment and vandalizing her possessions. The evidence keeps vanishing before she can show it to Nick, who grows concerned that she’s slipping into the same delusions that afflicted Stella. When Catherine finds Stella’s diary, she learns that Stella suspected Nick of infidelity. The diary reveals Stella’s jealous rage and her revenge-seeking impulse—she destroyed possessions belonging to the suspected mistress, yet the evidence always disappears before it can be presented. Desperate for answers, Catherine confides in Charlie that she believes Stella may still be alive; Charlie suggests a wormhole might allow Stella, who exists in the past, to interact with Catherine in the present.
Catherine digs deeper, reaching out to Stella’s twin sister and ex-husband. Both confirm that Stella was jealous of an unknown woman—one Catherine comes to believe is herself. After Daisy and Charlie die under suspicious circumstances, Catherine borrows Badge’s pistol, a German-made model imported specifically for her situation. The tension crescendos when Stella’s diary—missing for a time—reappears with a new entry in which Stella threatens to murder Catherine by name. Nick finally believes Catherine, and they prepare to stay at a hotel, though Nick leaves to meet her there. While Catherine packs, Stella launches a brutal assault with a pair of scissors. In a tense struggle, Catherine shoots and kills Stella in self-defense.
Back in the police station, Catherine is booked and faces a psychiatric evaluation, but she recalls that the pistol used could be traced. With no conclusive evidence and skepticism about the wormhole theory, the police release her with a warning not to waste their time. From a distance, Stella watches as Nick and Catherine embrace, a quiet reminder of jealousy that time can’t erase.
