Jeanne Deber, infamously known as “La Mante,” was a notorious serial killer who struck fear across France over two decades ago. Now, the police compel her to leave her seclusion to help catch an imitator following in her footsteps. She consents to assist, but with a single stipulation: she will only communicate with one person, her son Damien Carrot. Damien, who pursued a career in law enforcement due to his mother’s heinous acts, has avoided any interaction with her since she was apprehended.