Dono, a singer in a struggling U2 tribute band, takes a job in a head shop in Dublin, 2010. After he and his mentally damaged friend, Cormac, win a shady lottery draw, but accidentally smoke the winning ticket, they find themselves in debt to their gangster boss, Pauly. Pauly, the "Head Shop King" of Dublin wants revenge on some illegal dealers for burning down one of his head shops, so decides to send Dono and Cormac on a mission to find the dealers' base and burn it down. However, Dono soon uncovers an evil plot to destroy the whole country with dangerous, experimental drugs and realizes that he is the only one who can stop it.