Claire, a middle-aged professor of French literature, shares custody of her two sons with her ex-husband Gilles. She carries on a casual affair with the emotionally distant Ludovic, who on one occasion lets his roommate Alex pick up his phone when Claire calls. Claire develops a fascination with Alex, whom she has only seen on social media. She creates a fake persona, "Clara Antunes", on Facebook and connects with Alex, gradually developing an emotional affair with him. When Alex grows insistent upon meeting in person, Claire decides to call off the affair rather than risk him being disappointed with her middle-aged self. Alex deletes his profile, leading Claire to meet with Ludovic to find out about him. He tells her that Alex, broken-hearted over a girl on Facebook, has taken his own life. These narrative details are interspersed with a series of psychotherapy sessions between Claire and Dr Bormans. Bormans asks Claire to be honest about a detail in her story that does not add up, leading Claire to disclose that the photos and videos of "Clara" used during her communications with Alex actually belong to her estranged niece, Katia, whom Gilles had left Claire for. Bormans receives a dossier from Claire containing a story in which she makes Alex' acquaintance after the end of the "Clara" persona. In the story, Alex and Claire become live-in lovers, but a nagging doubt over whether "Clara" retains a place in his heart leads Claire to revive the persona and ask Alex for a meeting. Alex, torn, chances upon the alternate phone she used for "Clara"; confronting Claire at a tea shop, he unnerves her to the point where she distractedly walks into traffic. Bormans concludes from the story that Claire is unwilling to allow any happiness to herself, even in a work of fiction. Claire proceeds to an in-patient institution for treatment of a mental disorder. Later, Bormans decides to ask Ludovic for information about Alex, and learns from him that Alex' death was a ruse of his making. Having heard "Clara's" voice in one of her calls to Alex, Ludovic had realised what Claire was doing and decided to step in to protect his friend. Dr Bormans brings this information to Claire, who is now ready to leave the institution. In a twist ending, she dials Alex' number from "Clara's" phone.
