A mercenary band fights to get refugees and a fortune in diamonds out of the Congo.

In 1960, Capt. Bruce Curry, a mercenary, leads a Congolese troop and a small crew of his own men--Sergeant Ruffo, a Congolese patriot educated in the United States; sadistic ex-SS officer Henlein; young Belgian officer Surrier; and the alcoholic British Dr. Wreid--into the Congo aboard a train. Their mission is to rescue the white inhabitants of Port Reprieve, which is about to be attacked by rebel Simba soldiers, and also to bring back uncut diamonds valued at millions of dollars for Congolese President Ubi. En route, Curry and his men rescue a blonde Belgian refugee named Claire and stave off a series of attacks by an enemy plane. When the train arrives at Port Reprieve, the group learn that the time vault containing the diamonds will not open for another 3 hours. In the interval, Wreid attends an African woman in childbirth and decides to stay with his patient rather than escape. Finally, the diamonds and refugees are loaded aboard the train, but the Simbas uncouple the coach containing the diamonds just as the train pulls out. Curry and Ruffo lead a commando raid to retake the town. Though Surrier and Wreid are killed, the raid is successful, but on the way to a nearby town the group almost run out of gas. Curry uses what little gas is left to go on and radio for help, leaving Ruffo, Henlein, Claire, and the refugees behind. Henlein, mistakenly believing that Ruffo has the diamonds, kills him and then flees into the jungle. When Curry returns and finds his friend dead, he pursues and brutally kills Henlein. Curry then returns to Claire and the refugees, and with Ruffo's principles in mind, he surrenders his authority to the native corporal and turns himself in for court-martial.