20+ years after her arrest, the female serial killer known as The Mantis agrees to help French police capture a new killer who is replicating the original killings. But only if her son (currently a vice squad detective), heads the investigation.
The show is mostly an excavation of past secrets, with some decent twists and turns as they try to capture the copycat killer . . . and whoever might be responsible for manipulating them.
Pretty good psychological thriller.