Scobie, Deputy Commissioner of the Sierra Leone Police in Freetown during the Second World War, is unhappily married to fellow-Catholic Louise: both mourn the death of their only daughter. Despite his having been a police officer in the country for 15 years, when the Police Commissioner announces he is to retire, Scobie is overlooked in favour of a younger man sent out from the UK.
On a search of a neutral Portuguese ship, the Esperança, he finds an envelope addressed to Germany. When he confiscates it, the captain begs him to do nothing because the letter is to his daughter. Feeling pity, Scobie burns it. His wife does not like the climate or the other expatriates and keeps begging him to let her go to South Africa by sea but they cannot afford the fare. Eventually he accepts a loan from Yusef, a suspected smuggler.
Called up country because a local District Commissioner is in trouble, he finds the man has committed suicide because of his debts. While he is there, survivors of a ship torpedoed by the Germans are brought ashore by the Vichy police of neighbouring French Guinea. One is Helen, a young widow who reminds him of his dead daughter. Back in Freetown, he finds she has been given a hut near his house and, after he pays her a visit, they commence an affair. After an argument, he writes her a love letter but it is intercepted by a servant in Yusef's pay.
He learns that Louise is returning and Yusef tells him that he must give a packet of contraband diamonds to the captain of the Esperança or he will give his wife his letter to Helen. He complies. However, someone tells Louise about the affair.
Scobie is in torment between his love for Helen and his responsibilities to his wife, his wartime role and particularly his religious faith. He contemplates suicide but is then killed trying to stop a brawl.
The main difference between the film and the book is in the ending, which is almost equally bleak, but reversed from Greene's original story. In the book, Scobie's servant is killed (apparently an act of revenge by Yusef, here played by Gérard Oury). Scobie commits suicide. In the film, Scobie intends to kill himself, but is interrupted by a fight breaking out. He intervenes and is shot. The servant (Earl Cameron) does not die, but instead Scobie dies in his servant's arms.
References
^Vincent Porter, 'The Robert Clark Account', Historical Journal of Film, Radio and Television, Vol 20 No 4, 2000 p501