Three adventurers fight the slave trade in turn-of-the-century Africa.

In 1897 engineer David Moore is sent to Equatorial East Africa to plan a new railway route. Accompanied by young Brian Ferrers, the nephew of the railroad firm's owner, he arrives in Edwardstown. Jack Cuortemayn, an old white hunter whom he expected to lead the safari, refuses to guide them to the railroad site because of his opposition to anything that might change the Africa he loves. Cuortemayn and mission worker Ruth Knight warn Moore that he should not start his trek until a band of slavers leave the area. Moore ignores their advice, and he and Brian lose their way in the wilderness. After they are rescued by Cuortemayn and Ruth, a romance develops between Moore and the young woman. Distrustful, Cuortemayn offers to lead Moore to the railroad site if he will promise not to see Ruth again. Ruth overhears the conversation, sets off for the mission hospital, and is captured by the slavers, who take her and a group of native captives to a secret mountain hideout where they are to be sold to Arab slave traders. Moore, Cuortemayn, and Brian unite to save her; their surprise attack catches the slavers unaware; and Brian seals their fate by dynamiting them inside a cave. The safari then regroups, this time to head for the site of the proposed railroad.