In a Britain which has been invaded by the Nazis and living under occupation for several years, Frank is injured in an ambush attack carried out by the group of freedom fighters to which he belongs. Lying wounded on the ground, he is found by a young girl who takes him to her family's sprawling family mansion. Before he knows it he is a prisoner - she keeps him locked in a room, unbeknownst to the rest of her family. Then Frank discovers that the family are Nazi collaborators - and realizes he is in terrible danger...