12-year-old Mully (Charlie Reid) has lost his mother, and catches his debt-ridden father stealing the charity money they've raised in her name. Grabbing the cash, Mully steals a taxi and is shocked to find a woman, Joy (Olivia Coleman), in the back seat with a baby. A straight-talking solicitor who didn't expect to get pregnant, Joy is struggling with motherhood and planning to give her baby away to a friend. Desperate to escape and leave her life behind, she joins Mully on a wild journey across Ireland, stealing cars, hitch-hiking, catching ferries, and breaking police barricades, with Mully's father in hot pursuit. As these two lovable rogues gradually bond over their complicated feelings towards their parents, they learn to find friendship and love in each other.