After his daughter Justine is founded beaten, raped, and murdered in a local park, Dr. Bruno Hamel (Claude Legault) find his life shattered beyond repair. On news that a suspect, Anthony Lemaire (Martin Dubreuil) has been arrested under ironclad evidence, Hamel abducts him police custody, feeling even the max sentence isn't enough for what Lemaire has done to his child.
Breaking into an unoccupied cottage in the woods, Hamel takes Lemaire there, and proceeds to torture him. Lemaire at first denies what he did, only to later admit to Justine's rape and murder. He even admits to the rapes and murderers of three other girls, in an effort to enrage Hamel to the point of killing him swiftly. However, he does not realize Hamel intends to torture him for seven days and then kill him on what would have been Justine's birthday.
Hamel leaks the names to the press, and finds support with two of the families. However, a third woman, Diane Masson (Pascale Delhaes) claims to be over her pain, and that Lemaire "doesn't exist" for her. Enraged, Hamel kidnaps her and forces to see her child's murderer. When Diane says every time Hamel tortures Lemaire, he is just killing Justine again, Hamel knocks her out and leaves her outside a shop.
By this point, the seventh day arrives. Police have figured out where the cabin is. Hamel comes out, having decided not to kill Lemaire. As he is led to a cop car, a reporter asks if he thinks vengeance was right. Hamel says no. When he is asked if he regrets anything he did, Hamel also says "No."
Thanks Tim (Spectre)!