In the Straits of Sembaleng, five men are dispatched by submarine in Klepper canoes to rescue survivors of a shot-down plane on a nearby island which is occupied by the Imperial Japanese Army. Led by Paul Kelly (Gibson), an inexperienced commando officer, the team secretly lands on the island and hides their kayaks. As they venture in land, Ted 'Kingo' King is hit by fire from an unseen machine gun post, the team quickly eliminates the Japanese defenders and return to their wounded comrade. King has been hit on the leg, the bullet smashing his kneecap. King cannot be allowed to fall into enemy hands and compromise the mission under interrogation, and after sharing a cigarette with him, Costello shoots him. The four remaining men return to their search; coming across a rice farmer, they learn of the area in which the plane crashed. The rice farmer is also killed in order to preserve secrecy.
But as they near their destination they spot a Japanese squad at a local house, after the Japanese leave they enter the house and meet the local resistance leader Lin, his grown up daughter Chien Hua and her younger brothers and sisters. With a guide to lead them, they head off to the plane but are attacked by Japanese soldiers at a Buddhist temple. Separated from the rest, interpreter Jan Veitch ends up returning to Lin's house where Chien Hua hides him from the returning Japanese. After the deaths of their soldiers, the Japanese officers Watanabe and Imanaka torture Chien to tell them the location of her father, who they believe is hiding the survivors of the crashed plane, but Chien Hua refuses. Lin's son Shaw Hu falsely tells the Japanese that Lin, the Z men, and the plane's survivors are heading for the island's capital. All the Japanese leave except for two soldiers guarding Chien Hua; Veitch kills both with help of Shaw Hu.
Meanwhile, within sight of the plane, Kelly watches as locals blow up the wreckage. Lin is evasive, and after quizzing the inhabitants of a village, the team head on to the plane. Kelly manages to get Lin to tell them that the two survivors are being taken to his home, so they turn around and head back. In the capital, Veitch is led to the survivors. One of them is a defecting Japanese government official Imoguchi, and he is believed to hold a secret that could end the war faster. Only Kelly knows that he must be rescued at any cost - or killed. As the pieces of the puzzle begin to fall together, Kelly must persuade his own men that Imoguchi is worth rescuing and the local resistance that it is worth fighting against their Japanese enemies.
