A 13-year-old Welsh boy carefully charts the experiences of his adolescence through his secret collection of hand-made maps. Griff's maps are a blend of actual locations and those of the local Celtic myths; they are for him, a sort of diary, a means by which he makes sense of his world and the disturbing mysteries of late, most of which center around the disappearance of Alis, the star pupil of Griff's mother, who owns a dance school. He also charts the many affairs of his father. Griff has a sister Ruth, but he is really only close to his mother, Megan. Griff decides to investigate the disappearance of Alis, and enlists the aid of Joseph, a Polish vagabond who seems to know what happened. This British drama chronicles their attempts to discover the truth, which in the end turns out to be a painful experience.