Based on H. Rider Haggard's novel, English hunters follow the Irish trying to find ancient diamond mines in Africa.
In 1881 Kathy O'Brien (Anna Lee) and her father Patrick O'Brien (Arthur Sinclair) at the busy diamond mines get a ride with Allan Quartermain (Cedric Hardwicke). Kathy tells Quartermain that she dislikes hunting. At night they find Umbopa (Paul Robeson) and a map to King Solomon's mines. Patrick copied the map and left. Umbopa won't work for Quartermain, who takes Kathy in his wagon. Quartermain meets hunters Sir Henry Curtis (John Loder) and Commander Good (Roland Young). Umbopa helps Kathy take the wagon, but Quartermain pursues them. Umbopa sings "Walk, Walk" as they go. Quartermain finds Kathy in the desert, and Henry suggests they go with her after her father. They walk with packs across the sand. They find Patrick's wagon and are low on water. They lie down during a sandstorm. Then Umbopa smells water and finds it.
They reach the mountains, and Umbopa sings "Climbin' Up." They eat melons. When they meet natives, Umbopa translates. They meet the chief Twala (Robert Adams), and Quartermain interprets. The ancient witch doctor Gagool (Sydney Fairbrother) has the boulder rolled away from the mine. After a scuffle Quartermain fires his rifle, and the natives run. Umbopa found Patrick's medallion. Others want to leave, but Umbopa refuses and claims he should be king instead of Twala. Umbopa reveals his tattoo, and the elders bow. As native warriors dance, Good notes an eclipse will soon occur. Gagool picks out three men, and the warriors kill them. When she picks Umbopa, Quartermain shoots at the warriors and points to the sun, warning them. During the eclipse the natives panic, and Umbopa sings.
Afterward warriors march to Umbopa's stockade. Quartermain shoots as they attack. Umbopa's tribe fights them. Henry fights Twala hand to hand and kills him. Umbopa is given his necklace and is cheered. In the mine Kathy finds her father with a broken leg. Henry, Good, and Quartermain enter the mine, and Henry embraces Kathy. Gagool starts a fire and is buried by falling rocks. Patrick shows his diamonds. The volcano erupts; Henry and Kathy say they don't mind dying. Umbopa and Henry push away a boulder so they can get out before the mine collapses. King Umbopa sends guides with Quartermain's return party and sings "Climbin' Up."
Filming with authentic African tribes added some realism to this rather fantastic story of an African prince reclaiming his heritage at the site of a fabulous mine. While Henry romances Kathy, Good covers his fear with witty quips while the reluctant Quartermain is led on by Kathy's zeal.