A key antagonist who operates under an assumed identity, Katinsky meticulously maintains a facade throughout the story. His long-term plans intersect with the main plot, providing a mysterious and strategic counterpoint to the protagonist's endeavors.

An ostensibly offensive and unkempt figure, Lamb runs Slough House with an unconventional but effective style. His experience in espionage and unique methods play a crucial role in the happenings around him, offering unexpected depth to his character.

A young, ambitious member of Slough House whose career aspirations are influenced by his family's legacy in the intelligence community. His eagerness for adventure and validation often leads him into complex scenarios.