The R of the title stands for the young protagonist, Rune, fearlessly played by Pilou Asbæk. Imprisoned for violent assault, he's a cocky, good-looking young man placed in the hardcore ward, where his survival depends on quickly learning the prison's parallel world of rules, honor, and obligations. R also stands for Rachid, a young Muslim prisoner who becomes Rune's friend and accomplice, defying the rigid racial stratifications among the inmates.

A custodian in a housing project discovers that a naked, mute woman he found in one of his apartments has miraculous healing powers.