Boris Turganev, a Russian physicist attending a conference in England, requests and is granted political asylum there. He is permitted to continue his research at Barfield, a British nuclear experimental laboratory, where he passes secret files to Paul Skelton, a wealthy local landowner. Leila, Turganev's assistant, has a narrow escape when she discovers that he and Skelton are spies, although Turganev is actually working for British Intelligence and is feeding false information to the traitorous Skelton. It is arranged for Turganev to be caught spying, stand trial, and be condemned in order to allay suspicion. A prison escape is engineered so that he can return to his own country and continue his espionage work there for the British government.