Maureen (Louisa So) has sacrificed her youth and her prospects in order to take care of her ailing mother, Mag (Deanie Ip), for the last two decades in a rundown house in the small town of Leenane, in Galway, Ireland. When Maureen attends a party against Mag's wishes, she brings home Pato (Poon Chan-leung) and the morning after, a huge fight breaks out between the two women. Mag does everything she can to sabotage the fledgling romance, and when Maureen pieces together the extent of her mother's interference, the tensions between the two women explode.