SOLVED. French book about a prison guard

[Caroline]

he is a prison guard who lives alone. One day he meets a prisoner who is seen as dangerous and he starts to talk with him. The guard learns that the prisoner has killed his wife. The guard is depressed and wants to relive the murder so he returns to the scene of the crime described by the prisoner. The novel is quite dark.

[Caroline]

I found it : Où se perdent les hommes

[SamSpayedPI]

Où se perdent les hommes for the link.