Samuel Sayer and his sister Rose are British Methodist missionaries in the village of Kungdu in German East Africa at the beginning of World War I in September 1914. Their mail and supplies are delivered by a small steam launch named the African Queen, helmed by the rough-and-ready Canadian mechanic Charlie Allnut, whose coarse behavior they stiffly tolerate.
When Charlie warns the Sayers that war has broken out between Germany and Britain, they choose to remain in Kungdu, only to witness German colonial troops burn down the village and herd the villagers away to be forcibly recruited. When Samuel protests, he is beaten by an officer, and becomes delirious with fever and soon dies. Charlie returns shortly afterward after having found his mine to have been destroyed by the Germans and being chased for his supplies, which include gelatin explosives. He helps Rose bury her brother, and they set off in the African Queen.
While planning their escape, Charlie mentions to Rose that the British are unable to attack the Germans due to the presence of a large gunboat, the Königin Luise, patrolling a large lake downriver. Rose comes up with a plan to convert the African Queen into a torpedo boat and sink the Königin Luise. Charlie points out that navigating the Ulanga River to get to the lake would be suicidal: they would have to pass a German fort and negotiate several dangerous rapids. But Rose is insistent and eventually persuades him to go along with the plan. Eventually Charlie becomes inebriated and drunkenly insults Rose and her plan, who retaliates by dumping his supply of gin into the river.

Directed by John Huston
Starring Humphrey Bogart, Katharine Hepburn, Robert Morley