We first meet Archer in 1941, with the vast majority of England and Wales are under Nazi occupation after losing the Battle of Britain. Pockets of resistance continue to show their defiance against the occupying German forces, but after a German pilot is murdered by a British Resistance fighter, tensions in London could not be higher.

Finding the missing atomic bomb documents becomes Archer's main priority as he frantically tries to track down the elusive Dr John Spode. Still a target for the Resistance, Archer faces a fatal tussle on the underground and a deadly explosion at Highgate Cemetery.