Alec is a seasoned British Intelligence agent running spies in East Berlin. He projects a gruff, deeply cynical exterior that masks a profound weariness from a lifetime spent in the shadows. Following the collapse of his intelligence network, he relies heavily on alcohol and struggles to adapt to the bureaucratic elements of the "Circus" in London. He accepts one final mission to strike back at the East German intelligence apparatus.

Liz is a young librarian and dedicated member of the British Communist Party. She possesses an awkward physical presence that wavers between plainness and beauty. Her sincere belief in humanistic progress contrasts sharply with the cynical environment of espionage, making her both empathetic and highly vulnerable to manipulation. She provides Alec with food, medicine, and companionship during his lowest moments.

Mundt is a formidable East German intelligence chief with a background as a former Nazi. He operates with extraordinary self-confidence and a chilling calmness, commanding terror even among his own agents. His face lacks humor entirely, marked by frighteningly direct eyes. He heavily favors violent elimination over careful interrogation to secure his position.

Fiedler is an intelligent, Jewish deputy within the East German intelligence apparatus. Unlike many of his peers, he espouses communist ideology with absolute sincerity. He approaches his work methodically, treating intelligence gathering like tending a garden, and frequently engages his subjects in philosophical debates about morality, belief, and the common good.

Control is the mild-mannered head of foreign intelligence for the British "Circus." He dresses plainly, often wearing a shabby brown cardigan knitted by his wife. Despite his unassuming exterior, he orchestrates complex operations with detached pragmatism, openly viewing morally suspect tactics as necessary defensive measures in the Cold War.

Karl is a former Wehrmacht soldier who serves as Alec's most valuable intelligence source in East Germany. He holds a position within the Praesidium of the East German Communist Party, allowing him to pass highly sensitive information regarding communist state activities to the British.

George is a retired British intelligence spy who previously survived an assassination attempt orchestrated by Mundt. He operates quietly in the background of London's espionage world, occasionally checking on civilians connected to active Circus operations.

Peters is a professional Soviet KGB officer tasked with interrogating potential defectors. He is highly skilled and cautious, carefully weighing the authenticity of the intelligence he receives while probing for inconsistencies in a subject's story.

Ashe is a low-level communist agent operating in Britain under the guise of a writer for foreign presses. He employs overly intricate and implausible cover stories to approach potential targets, seeking to recruit vulnerable individuals for his superiors.

Sam is a well-connected agent for a communist government operating in Britain. He acts decisively to secure valuable assets, arranging passports and international travel to extract defectors from London to the European mainland.

Miss Crail is an ill-tempered librarian who strictly enforces petty rules. She spends much of her workday calling her mother to complain about minor grievances, reacting with quiet fury when her employees act unprofessionally or take long lunches.

Elvira is Karl's mistress. She possesses dangerous knowledge regarding his espionage activities, which deeply worries his British handlers.

Karden is a sharp legal mind working within the East German state apparatus. He questions witnesses methodically to dismantle opposing arguments and expose the personal motivations of those testifying against his client.

The President is the head judge of the East German tribunal. He maintains a gentle but firm demeanor when questioning civilians, balancing state requirements with judicial process.

The Commissar is a staunch political officer working in the East German prison system. She views all inmates as obstacles to socialism and openly expresses harsh, prejudiced views regarding state enemies.