Franny is a cleaner at a Galway university when she sneaks into one of Professor Niall Lynch’s lectures about birds. Birds are one of her passions, along with wandering and the sea. Not long after their next encounter, they marry, but Franny can’t stop wandering, and Niall is depressed by the destruction by humans who’ve caused most animals to become extinct. Franny is on a pilgrimage to follow the last remaining birds — the Arctic terns — from the northern hemisphere to Antarctica. She meets Captain Ennis who unwillingly allows her board his ship in Greenland. But Franny has demons — she sleepwalks, and memories of a life in Ireland haunt her. Will there be any terns left if she reaches Antarctica? And can she find solace from the secrets she keeps about her criminal past?