The Human Factor is a 1979 film directed by Otto Preminger.
Maurice Castle (Nicol Williamson) is an operative in the British spy agency MI6, working in the Africa section. He is hardly James Bond but instead is a worker bee with an office and a desk, and he has to share the office, with a fellow named Davis (Derek Jacobi). In the past however he worked in the field in South Africa, and from South Africa he brought back a wife (Iman, the supermodel, in her film debut) and an adopted son, Sam.
A South African intelligence officer arrives in England for a joint operation, and brings word that there is a suspected leak in MI6. Castle's superiors, Hargreaves and Dr. Perceval, get Daintry from internal security (Richard Attenborough, in his last acting role until Jurassic Park 14 years later) to hunt for the mole, but Hargreaves and Perceval themselves zero in on Davis—he's single, he drinks a lot, he likes strip clubs, he just generally fits their preconception of a mole.
Naturally, it's actually Castle who is the mole. He's been passing info on to the Soviets for seven years, not for money or for ideology, but for personal reasons that date back to his service in South Africa.
Otto Preminger's last film, an adaptation of a novel by Graham Greene. It was a Troubled Production in which Preminger had to sell a house and some art work to fund the film himself after his backers pulled out. John Gielgud appears in one scene as Watson, Castle's supervisor at the agency.
- Affably Evil: Dr. Perceval is a jolly and friendly man who loves fly fishing and socializing over a drink with friends. He also has absolutely no qualms about poisoning an MI6 agent suspected of leaking secrets to the Soviets, and shrugging off the agent's death as no great loss when he realizes that he's murdered the wrong man.
- Black-and-Gray Morality: Castle is, as he himself admits, a traitor. But he is in debt to the Soviets after using them to get his wife out of South Africa. He is far more sympathetic than Hargreaves and Perceval, who coolly murder poor Davis in order to spare the agency embarrassment, and aren't even all that sorry when they find out they killed the wrong man.
- Blowing Smoke Rings: Just to illustrate his sociopathic indifference, Perceval blows smoke rings while he and Hargreaves discuss murdering Davis in order to spare MI6 from bad publicity.
- The Book Cipher: Castle communicates with his KGB handlers by means of books that he buys from a used bookstore. It turns out that the genial old man who owns the bookstore is also a KGB spy.
- Could Say It, But...: Castle and Daintry have a loaded conversation in which Castle says that Davis couldn't have possibly been the spy, that he didn't even know anything about South Africa. Castle meaningfully says that if there was a leak it would most likely be someone who served in South Africa (like Castle did) and has a personal connection to South Africa (like Castle does).
- Diplomatic Immunity: As Mueller explains in a flashback, this is the only reason Castle wasn't arrested for having a black girlfriend.
- Double Agent: Castle admits to his wife that "I've been a double agent for seven years." While still doing his spy stuff for MI6 he has also been feeding the KGB intel, mostly low-level stuff.
- Downer Ending: Castle is stuck in Moscow, in what appears to be glorified house arrest in a dingy apartment. He is likely to be permanently separated from his wife, as Perceval tells her that if she tries to leave Britain, she'll be investigated for possible involvement in her husband's espionage—and the boy can't leave anyway as he doesn't have a passport. Castle tells his Moscow contact that he'd rather have stayed at home because at least jails have visiting hours. The film ends with tears rolling down his face as he talks with Sarah on the phone.
- Fake Defector: A little Kick the Dog moment at the end. Castle's KGB sponsor in Moscow reveals that the intel Castle has been passing for seven years actually had no importance at all. MI6's mole in Moscow (whom the audience never sees), the one who reported the leak in the Africa section of MI6 in the first place, isn't a real mole. He's been passing Castle's intel right back to MI6 to prove his bona fides, while also passing back disinformation meant to confuse British intelligence. That was the only value Castle had, as a pawn to convince the British to trust the fake mole.
- Flashback: A series of flashbacks explain why Castle became a mole. He fell in love with his wife Sarah in South Africa, but thanks to racist apartheid laws against miscegnation, she was subject to arrest and imprisonment just for dating him. Castle got a KGB contact of his to smuggle Sarah out of South Africa to safety, which put him in their debt, which is why he spies for them.
- Karma Houdini: Naturally, Perceval and Hargreaves get away with the murder of Davis.
- Make It Look Like an Accident: Perceval kills Davis with an injection meant to simulate death by natural causes.
- The Mole: Castle is a mole, an MI6 agent leaking to the KGB.
- Not What I Signed Up For: Daintry, who is dedicated to finding the mole but is shocked and disgusted when he realizes that Perceval murdered Davis. Daintry doesn't get any less disgusted when he finds out that Perceval killed the wrong man.
- Sexy Secretary: Davis lusts for Cynthia, the hot secretary that he and Castle share.
- Spy Fiction: Stale Beer flavored. Graham Greene said of his novel that he had set out to write a spy thriller that didn't have any James Bond-style violence or derring-do, but instead portrayed spies as civil servant office drones.
- What You Are in the Dark: Castle has the chance to retire from spy work, and in fact he does sever contact with the Soviets, after Hargreaves and Percival incorrectly tab Davis as the mole and murder him. But when he finds out about the British-South African operation, "Uncle Remus"—placing tactical nuclear weapons on South Africa's border, as security in the event of a race war—he leaks that plan to the Soviets, and thus has to flee the country.
- You Can Leave Your Hat On: Castle, Davis, and Hargreaves go to a strip club in a scene that is basically an excuse to have a Fanservice Extra stripper.