In the war-torn London of 1939, fourteen-year-old Hazel and five-year-old Flora are evacuated to a rural village to escape the horrors of the Second World War. Living with the kind Bridie Aberdeen and her teenage son, Harry, in a charming stone cottage along the River Thames, Hazel fills their days with walks and games to distract her young sister, including one that she creates for her sister and her sister alonea fairy tale about a magical land, a secret place they can escape to that is all their own.