TV. 2017.

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.