During the 1950s, American adventurer Matt Campbell arrives in Kenya to join his brother George. George wrote to Matt and urged him to come to Kenya where a very lucrative business opportunity has arisen. After checking himself in a hotel, Matt is visited by a local missionary, by the name of Ralph Hoyt, who informs Matt that his brother George has recently been killed by a member of the Leopard Men religious cult. The cult's aim being the extermination of the White man in Africa. Matt also meets the missionary's pretty niece, anthropologist Ann Wilson and big game hunter Gil Rossi, a Frenchman who was George's business partner. Rossi implies that he, George and a man named Elliott Hastings jointly owned a mine in the bush country beyond Mombasa. Apparently, the mine contained something more precious than gold. However, missionary Ralph Hoyt tells Matt that the mine is most likely worthless and tries to dissuade Matt from seeking the mine. Nevertheless, a funeral for George is planned and they all prepare to travel in the bush country to where Elliott Hastings and George were when George was killed by the mysterious Leopard Men. Matt Campbell is anxious to retrieve his brother's body for burial and also to find out who killed George and why. Given the fact that, at the moment, Kenya is going through the Mau Mau rebellious uprising of the Kikuyu tribes, Matt is not sure of who killed George. Besides, he really wants to know where George's mine is and what it really contains.