Writer and director Peter Mullan portrays the barbarities of Ireland’s Magdalene laundries, a network of institutions run by the so-called Sisters of Mercy, where “wayward” women were bound into virtual slavery in open-ended sentences, sometimes for no more than flirting with boys or being victims of rape. (The last of the laundries closed in 1996; the church reportedly has shelled out millions in reparations.) The sadistic horror of the story fuels the film the way some World War II movies feed on the Holocaust, but the movie is dramatically stagnant, and Mullan substitutes grimness for power. Performances are expert, although the characters merge into the melodrama of Mullan’s Dickensian social outrage. Standouts are Geraldine McEwan as the awful mother superior and Eileen Walsh as a simple-minded inmate.