With one war ended, a new one is looming as the iron curtain falls across Europe. Suspecting that British atomic research has been infiltrated, MI5 asks Foyle to investigate the possibility of a Russian spy network in the heart of London. During his inquiry, Foyle learns that his former driver, Sam, has been working for one of the possible suspects. Could she be involved?
Masterpiece Mystery: Foyle's War, Series VII, Sunday at 8 p.m.