Samuel spies on his new friends while his relationship with Kathleen intensifies. Hannah and Kathleen investigate Anthony’s disappearance.

Kathleen visits the boarding house in search of Anthony, but has no luck. Armstrong explains to Samuel that they have reason to believe that people connected with the Shaw family could be enemies of the state. Not knowing who to believe, Samuel confronts Mr Field.

The secret service tasks Samuel with spying on the Shaws in exchange for an order of his invention, and Hannah discovers that Kathleen has a tragic family secret.

Samuel learns the truth about the Shaws and the MI5 men. His is invited to an extraordinary secret meeting, while Hannah becomes increasingly worried about her father’s safety.

During the tumultuous summer of 1958, Samuel prepares to launch his new invention, which is attracting some suspicious followers, before meeting the mysterious Kathleen.

After the shooting, Field places the Petruhkin home and factory under protection. Samuel makes his own plans and goes into hiding where he meets Kathleen in secret.