In Johannesburg, South Africa, adventurer Harry Jordan is asked by a native medicine man to help a young woman from Zululand whose husband, Stephen Timbu, has been accused of murdering a fellow gold miner in a drunken rage. When Harry goes to the police headquarters to examine the case records, Sgt. van der Cliffe shows him an enraged Timbu and his badly beaten cellmate. The evidence suggests that Timbu is guilty so Harry advises his wife to return home as there is nothing he can do. Later, Harry encounters Jan Reubens, an investigator for mining syndicates, who tells him that it is important for his current client to establish Timbu's innocence or guilt. Reubens explains that the man Timbu murdered was a member of a diamond smuggling ring, then pays Harry to resume his investigation. Harry goes to the mine where Timbu worked, talks with the manager, then goes underground to question Timbu's shift boss who knows him well. In a newly opened tunnel, Harry narrowly escapes death in a rock fall, which a friend of Timbu's says was no accident. Later, at a tribal dance, Harry finds a witness to Timbu's fight and learns that a part of a dancer's costume, a harness with bells, was found at the crime scene. As the dancers perform, Harry spots one with a torn harness and questions the man, from the Koza tribe, who runs off. Harry pursues him to the mine's waste materials dam, where he is captured and arrested. Although Timbu is released and rejoins his wife and baby, Reubens is unable to connect the murderer to the smuggling ring, but when he and Harry search the killer's shack they find an album with photos from a Rhodesian ranch owned by a man named Williamson, who Reubens suspects may be the leader of the ring. Reubens then sends Harry to Rhodesia to investigate Williamson, whom he meets by feigning an automobile breakdown. Williamson invites Harry to stay at his ranch where he explains that all of his native helpers have fled because of a lion in the area. Williamson, who has been drinking heavily, has killed many lions, but fears this one, as he believes that it has supernatural powers and is trying to avenge the deaths of the other lions. When Harry and Williamson go to track the lion, Williamson becomes fearful, prompting Harry to tell him that the lion will follow him the rest of his life unless he faces it now. Upon finding the lion, they discover that it is old and dying and surrounded by vultures. Williamson declines to shoot it but, when the lion suddenly attacks, kills it. Later, Harry questions Williamson about the Koza tribesman and learns that he was discharged for stealing by Williamson's foreman, Kennedy, who is now missing. Harry communicates the information to Reubens, who tells him that Kennedy's dead body has been found in Kimberley. Reubens now believes that Williamson was a false lead and sends Harry to Kimberley, where Carlton, the head of criminal investigation for the diamond mine, tells him that unpolished diamonds along with an address in Durban were found on Kennedy's body. Carlton provides Harry with a phony identity and asks him to pose as a friend of Kennedy and deliver the diamonds. Carlton's men intend to step in and arrest the recipient after Harry hands over the diamonds. At the Durban address, Harry is met by American Louise Saunders. When Harry tells Louise he has a package of diamonds for her, she does not take the bait and asks him to leave. However, later at his hotel, Harry finds Louise and her sinister accomplice Doc, a Nazi who performed experiments on prisoners of war, waiting for him with a gun. Louise informs Harry that she has checked his background and now wants the diamonds. As Harry has returned the diamonds to Carlton, he arranges to hand them over the following day. Police listen in as Doc examines the diamonds and offers to buy them for £2,000 to be paid later in the day at Louise's apartment. However, when Harry meets Louise she insists that they first go on a sightseeing tour of the city. In the Indian quarter, they get to know each other over a meal in a restaurant and although they embrace, Louise does not produce the cash. The next day, when Harry, faced with the dilemma of still having to entrap Louise, tries to avoid her, Carlton reminds him that she and Doc have left a trail of blood behind them. Harry arranges to meet Louise and Doc at the restaurant, where Doc is quietly detained by the police. With Carlton at an adjacent table, Louise invites Harry to leave with her for Europe and suggests that they can support themselves by selling narcotics. After Harry hands over the diamonds and receives the cash from Louise, Carlton arrests her. However, Doc escapes from custody and, as Harry and Carlton lead Louise down an alley, shoots at them. They return fire, killing Doc, then discover that he has fatally shot Louise.
