In a dingy cottage in Leenane, a remote part of Galway, spinster Maureen lives with her self-pitying, ruthless, hateful mother, Mag. Constantly at her beck and call, Maureen takes revenge by feeding her lumpy Complan and hurling the occasional insult. Escape comes in the form of Pato Dooley, who is about to go to Boston. When Mag interferes once too often Maureen decides the time has come to break free — in a very violent way.