Matt's mother kept all his childhood memories in a small box, amongst the many photos of Matt as a child. But something about those photos has always puzzled Matt. Is that really him? Why does he not remember those clothes and toys? And where, in the photos, is his sister Imogen?

Imogen, meanwhile, is living with her husband and their baby in a rented cottage. Ever since her childhood she has loved the Summer House, a charming folly in the grounds of a beautiful and ancient house on Exmoor, and now they have the chance of buying it. But the Summer House provides the key to the strange and tragic secret which has affected Matt's whole life.