Florence Nat (Annie Girardot) is a great lawyer at the Paris Bar. It was she who defended Simon Risler (Claude Brasseur), sentenced to death for the murder of an inspector from the Finance Brigade. A witness to the murder, Inspector Reynolds, accused Risler of a motive that is not true. So Risler decides to escape in order to extract the truth from Reynolds and it is with Florence Nat that he takes refuge. Florence will find a precious ally in the person of an old faithful friend, Alain Rivière (Bruno Cremer), a fallen surgeon who re-educates drug addicts in an isolated farm. But she will also find an enemy, Lucien Lebesque (Jacques Perrin), perfidious and intelligent investigator of the General Inspectorate of Services.