Showing Tom's Midnight Garden by Philippa Pearce

When Tom is sent to his aunt's house for the summer he resigns himself to weeks of boredom. Lying awake one night he listens to the grandfather clock in the hall strike every hour. Eleven . . . Twelve . . . Thirteen. Thirteen! Tom rushes down the stairs and opens the back door. There, awaiting him, is a beautiful garden. A garden that shouldn't exist. And there are children in the garden too - are they ghosts? Or is it Tom who is really the ghost . . .