Tom's Midnight Garden

Tom's Midnight Garden by Philippa Pearce

When Tom Long's brother Peter gets measles, Tom is sent to stay with his Uncle Alan and Aunt Gwen. They live in an upstairs flat of a big house with no garden, only a tiny yard for parking. The elderly and reclusive landlady, Mrs Bartholomew, lives above them. Because Tom may be infectious, he is not allowed out to play, and he feels lonely. Without exercise he lies awake after midnight, restless, when he hears the communal grandfather clock strangely strike 13. He gets up to investigate and discovers that the back door now opens on a large sunlit garden. Every night the clock strikes 13 and Tom returns to the Victorian era grounds. There he meets another lonely child, a girl called Hatty, and they become inseparable playmates. Tom sees the family occasionally, but only Hatty (and as is revealed later in the book, the gardener) sees him and the others believe she plays alone.