It is 1941 and the Germans have won the Battle of Britain. Detective Douglas Archer finds himself working under the brutal SS in occupied London. Archer investigates the murder of a black marketeer. When the glamorous US journalist Barbara Barga is spotted at the scene of the crime, Archer's gut feeling that this crime is far bigger than it would at first seem is confirmed, and he soon finds himself embroiled in a deadly plot.

An unexpected meeting with Himmler and Huth's boss, Professor Springer, underlines to Archer why the SS so desperately needs to track down the elusive Dr John Spode. When Archer finds himself unwillingly dragged into the resistance's plans, Huth endeavors to swing Archer's allegiance to the SS cause. Whose side will Archer choose?

With the army imposing martial law and a rounding-up of Resistance members, Archer faces life-changing decisions. Barbara's surprise proposal could provide a safe haven for Archer and his son, but can he really trust her with the country's most sought-after possession? Despite being caught in the middle of a battle between Kellermann and Huth, will Archer finally agree to help free the King?

Archer and Harry attempt to drive the king out of London, but things do not go to plan and Sylvia becomes an unlikely ally. Following a rough interrogation with a badly shaken Barbara Barga, Kellermann is hot on Archer's heels.