Jim Wormold is a middle-aged English expatriate selling Phastcleaners vacuum cleaners in Havana. Struggling financially after his wife left him, he seeks ways to support his demanding daughter. He accepts a lucrative offer from British Intelligence to work as a spy, despite lacking any aptitude for espionage. Mild-mannered and out of place in the tense political climate of Cuba, he applies highly unorthodox methods to fulfill his new intelligence duties.

Milly is Wormold's striking teenage daughter, whose Catholic faith heavily influences her daily routine. She swings between pious devotion and materialistic demands, famously buying a horse her father cannot afford. Her presence in Havana draws significant attention from local authorities, creating constant worry for her father.

Beatrice is a highly skilled typist sent from the London Secret Service to serve as Wormold's secretary in Havana. She carries the emotional weight of a faded marriage to a man who prioritized political ideology over their relationship. Practical and down-to-earth, she attempts to bring professional order to Wormold's disorganized espionage activities.

Dr. Hasselbacher is a German-born physician and veteran who has lived in Cuba for thirty years. He acts as a confidant to Wormold, frequently spending his time drinking at local bars rather than seeing patients. He holds a cynical view of the Cold War and encourages Wormold to disregard the strict demands of international affairs.

Captain Segura is the chief of police for the Vedado district in Havana. Known as "The Red Vulture," he maintains a terrifying reputation among the local populace for his brutal interrogation methods. He actively pursues a romantic connection with Milly, placing him in direct tension with her protective father.

Hawthorne is a recruiting officer for London's Secret Service. He operates with an aura of mystery, utilizing outdated spy methods like secret ink and literary codes hidden in copies of *Lamb's Tales from Shakespeare*. He recruits Wormold into M16, establishing him under the code name 59200/5.

Carter is an English expatriate who works for a rival vacuum cleaner company, Nucleaners. He initially presents himself as a benign, slightly coarse salesman who makes Wormold feel a sense of national kinship. He attends a European Traders' Association luncheon alongside Wormold, though his presence introduces unexpected complications.

The Chief heads the Secret Service operations in London. Operating entirely removed from the ground reality in Cuba, he reviews field reports and makes staffing decisions based on the supposed success of his remote agents.

Lopez is the local Cuban assistant at Wormold's Phastcleaners shop. He experiences frequent communication barriers with his British employer, leading to comical misunderstandings regarding business instructions and personal matters.

Rudy is a radio operator assigned to the Havana intelligence post by M16. He travels alongside Beatrice to set up the necessary technical infrastructure required for Wormold's communications with London.