This Man Must Die

A grieving father who channels his rage into a meticulously planned murder. He keeps a diary detailing his intent to kill the offender, exposing a fragile moral line between justice and vengeance. Throughout the pursuit, he vacillates between mercy and cold calculation, revealing a complex, obsessive personality. The decision to take action is as much about confronting guilt as punishing the guilty.

A detestable husband who exerts control over his wife and son, and who embodies the moral rot Charles believes lies behind appearances. He is charming yet vicious, a known womanizer who becomes the focal point of Charles's revenge. The possibility that he drove the fatal car aligns him with the diary’s planned order of events.

An actress who slept with Paul; She endures depressive anxiety and agrees to tell Charles more under pressure. Her trip to Brittany with Charles pulls her into the investigation’s emotional center, complicating loyalties. She becomes a key catalyst for the story’s revelations.

Paul’s teenage son who despises his father and fantasizes about killing him. He ultimately confesses to the murder to save Charles, becoming the moral pivot that upends the expected killer’s identity. His confession exposes how guilt can be weaponized to prevent further violence.

A police inspector whose investigation stalls and who confronts the possibility that the diaries and confessions are being used to derail the case. He plays a role in the suspicion that Charles orchestrated events, highlighting the limits of law in a world driven by private motives. His persistence frames the film’s procedural tension.

A member of the Decourt circle, whose exact role is not detailed in the summary but places the family dynamics under scrutiny. Her presence underscores the social consequences of Paul's actions within a close-knit circle.