London, 1886. Soho shopkeeper Verloc is paid by the Russian Embassy to spy on an anarchist cell. The Russians demand that Verloc orchestrates a bomb attack that will be blamed on the anarchists and provoke a British crackdown.

Michaelis' suspicions threaten to scupper Verloc's plans. Back in London, Heat faces the Professor's madness, and Winnie finds herself alone with Ossipon.

While Chief Inspector Heat struggles to makes sense of the plot behind the Greenwich bomb, Verloc returns home and attempts to hide the truth from Winnie.

With nowhere else to turn, Winnie seeks out Ossipon and places her trust in him. Heat and Stone go to Verloc's home to make an arrest.