This book is about a boy, Tom Long who goes to live with his Uncle Alan and his Aunt Gwen since his younger brother, Peter has the measles. His aunt and uncle live on a flat so there is no garden. Tom is sad and bored with only a few indoor games. One night he hears the old grandfatherclock, that belongs to old Mrs. Bartholemew strike unusually thirteen times. He gets out of bed and opens the back door in the hall and he finds a beautiful garden and he sets out to explore it and finds a funny letter adressed to the king of fairies. Oberon.

He keeps his discovery a secret and asks his aunt and uncle if lying is good and if they have a garden. Every night, Tom goes to the garden and soon befriends a lonely little girl called Hatty and they play together.

Soon Hatty has an accident while falling on a tree and she stays in bed for a long time. Sometimes, Hatty would grow faster when she had the accident and sometimes she was smaller.

One day, a grown up Hatty and Tom skated through Ely and they meet Tom’s brother, Peter and they skated back. Young Barty offers to give Hatty a ride and Hatty and Tom climb up and Haatty soon forgets about Tom and he becomes so thinner through that Hatty can wave her hands through Tom much to his annoyance.