`titreb“I am a prisoner, I can’t be a father !”`/titrebSetting up a discussion group, whose essential condition is safety and trust, in a prison environment governed principally by concerns for security based on surveillance and control is both a challenge and a paradox. This experiment is based on a shared experience of reliability which depends on the continuous participation of all those involved. Work around the function of instructions in the group was decisive. In this article we discuss the effects of the discussion group on the prisoners with regard to forming a paternal identity, as well as their reflections on transgression and their attitude to the law. The discussion group gives these fathers the sense of belonging to a group within the prison. Being a prisoner and a father becomes thinkable and reconcilable. These fathers take concrete initiatives in their relations with their child and their family. This discussion group for incarcerated fathers contributes fully to the prevention of a breakdown of family ties and of subsequent offending (recidivism).