In 1968 Saigon, Vietnam, Sergeants Buck McGriff and Albaby Perkins, agents of the U.S. Army Criminal Investigation Division (CID), investigate the murder of a Vietnamese prostitute whose baby was fathered by a U.S serviceman. Later, Buck and Albaby find an army solider named Maurice, who claims that the murderer is an American officer. When Maurice is killed while under police protection, Buck and Albaby report to their commander, Sergeant Dix, who informs them that six similar murders of prostitutes have occurred over the year, but high-ranking officials have stopped the investigations. At a nearby church, Sister Nicole, a French nun, tells Buck and Albaby that the six murdered women all had children with American servicemen. Buck and Albaby travel to the trenches, where former investigator, Sergeant Flowers, discloses that he had narrowed down the suspects to a few colonels, and gives them his files, including a photograph of a missing female witness, Nguyen. Returning to Saigon, Buck shows Sister Nicole the photograph, and she identifies Nguyen as the sister of an exotic dancer named Lanh. Nicole accompanies Buck and Albaby to question Lanh, but she refuses to speak to Americans. Later, Dix reports that three of the colonels on Flowers’s list were in Saigon on the night of the murder, including Colonel Dexter Armstrong. Buck and Albaby track Armstrong to the bedroom of a prostitute, but they are ambushed by his men, and knocked unconscious. Later, they awaken in the countryside, guarded by Armstrong’s unit. Ushered into a helicopter, Armstrong allows Buck and Albaby to question him, but when asked about the murders, Armstrong jumps out of the helicopter, committing suicide. Returning to the city, Buck and Albaby assume Armstrong was the murderer, report their findings to Dix, and are reassigned to California. Before leaving, however, Buck visits Sister Nicole and learns that Lahn and her child were murdered the night before. Realizing Armstrong was not the killer, Buck and Albaby want to resume their investigation, but Dix orders them to leave. While they travel with a military escort, two men appear and throw a grenade into the vehicle. However, Buck and Albaby survive and kill their attackers. As military police arrive, Buck escapes to Nicole’s church. As she cleans Buck’s wounds, she confesses the missing witness, Nguyen, is hiding in the jungle with Viet Cong (VC) soldiers. Through her contacts, Nicole sets up a meeting for Buck and Albaby to question Nguyen. Blindfolded, they are led by VC soldiers through a series of underground tunnels and show Nguyen the two remaining suspects from Flowers’s list, but she does not recognize either man. However, she sees a photograph of Dix and points to him as the murderer. Hurrying back to Saigon, Buck and Albaby search for Dix in his apartment and find evidence that his next intended victim is Nicole. As they arrive at the church, Dix aims his gun at them, but Buck and Albaby return fire and kill him.