In Paris, police search for a psychopath whose murders are inspired by Jeanne Deber, known as „The Mantis”, a famous serial killer who terrorised the country 20 years ago. Believing it takes one to know one, the police asks Jeanne Deber to help hunt the copycat. Placed in solitary confinement since her arrest, „The Mantis” agrees on one condition: to deal only with Detective Damien Carrot, her estranged son. Damien has no choice, for a serial killer is on the loose and could strike anytime, anywhere in Paris.