The series tells the story of Esther Lefèvre, a retired court clerk. But when she is diagnosed with early-stage Alzheimer's, a secret she had tried to bury deep in her memory resurfaces. She pulls a list of names from her archives and begins to eliminate, one by one, the people mentioned on it, transforming into an enigmatic and clumsy vigilante.
E1
Esther Lefèvre, a retired court clerk, is enjoying a peaceful retirement. But when she learns she has early-stage Alzheimer's, she decides, before she forgets everything, to confront a secret she had tried so hard to bury deep in her memory. Determined, she retrieves a list of names from her archives and begins to eliminate, one by one, the people mentioned on it. Meanwhile, police captain Célia Le Goff is investigating these serial murders.
E2
The unexpected arrival of Esther's daughter, Marianne, and her grandson, Milo, at her home for a few weeks, hinders the execution of her revenge. Celia discovers that the serial killer is leaving messages for her on the victims' bodies, but she doesn't understand their meaning.
E3
Esther is forced to kill the prime suspect in the serial murders, who had previously served as her scapegoat. She must dispose of the body without arousing the suspicions of Marianne and Milo. The murders are multiplying, and the police, on edge, have run out of solid leads. Removed from the investigation, Célia continues to delve into her past.
E4
Celia travels to her childhood village in search of answers. Esther's Alzheimer's, which is increasingly weakening her, means she doesn't have much time left before the end. Celia then receives a mysterious invitation from "The Cat", who invites her to a final confrontation.