When Tom is sent to stay at his aunt and uncle's house for the summer, he resigns himself to endless weeks of boredom. As he lies awake in his bed he hears the grandfather clock downstairs strike . . .eleven . . . twelve . . . thirteen . . . Thirteen! Tom races down the stairs and out the back door, into a garden everyone told him wasn't there. In this enchanted thirteenth hour, the garden comes alive - but Tom is never sure whether the children he meets there are real or ghosts . . .