British intelligence must convince Russian scientist Wilhelm Guttmann to come to the United Kingdom, but with his son in their hands, former soldier Johnny Donoghue is tasked with securing his cooperation amid Cold War tensions.

Donoghue goes undercover in Berlin to make contact with Guttmann and persuade him to defect, navigating tense East German surveillance and diplomatic complications between the British and West Germans.

Abandoned in East Germany as the operation unravels, Donoghue charges on with a desperate plan to smuggle Guttmann and his daughter across the border into West Germany.