Nine-year-old Frankie and his single mum Lizzie have been on the move ever since Frankie can remember, most recently arriving in a seaside Scottish town. Wanting to protect her deaf son from the fact they have run out of his father, Lizzie has invented a story which he is out at sea on the HMS Accra. Every couple weeks, Lizzie writes Frankie a makebelieve letter out of his father, telling of his experiences. As Frankie tracks the ship's progress across the world, he discovers that it is due to dock in his hometown. With the real HMS Accra arriving in only a fortnight, Lizzie must choose between telling Frankie the truth or finding the perfect stranger to play Frankie's father for just one day...