Summer 1940. As the cuckoo sings out across the Lake District, life is about to change for ever for local boy Tommy and his friend Sally, the mysterious evacuee girl who lives on the neighbouring farm. When they find a wounded Nazi airman in the woods, Sally persuades Tommy not to report it but to keep the German hidden. This starts a chain of events that leads to the uncovering of secrets about Sally's past and a summer of adventure that neither child will ever forget.