During the London Blitz of 1940, young Winifred is sent to join her sister in the English countryside to escape the horrors of the war. When she arrives, she encounters Edwin, a young eccentric boy, whose imagination and friendship provides her solace and companionship. They escape their reality by creating a world together in the woods. Castlewood is a coming-of-age exploration of escapism, grief, and what it means to be happy.