The term "SK1" is a codename given by the police to the first serial killer who was identified and arrested via DNA analysis in France.

[3] The film chronicles the hunt and trial of a 1990s serial killer, dubbed "The Beast of the Bastille".

The true story of Franck Magne, a young inspector starting out in the Criminal Investigation Department at 36 quai des Orfèvres, in the Crime Squad.

During it, Magne crosses paths with Frédérique Pons, a dedicated lawyer determined to understand the destiny of the man hidden behind this merciless killer.

The film plunges us into 10 years of investigation, amongst opinionated cops, determined judges, conscientious forensic policemen, and impassioned lawyers who will all be affected by this case that became the sensational "Guy Georges, the killer of Eastern Paris" case.