Tom Logan is the leader of the Philippine American Radio Communications Company, a group of allied radio engineers turned guerrilla fighters. They become trapped on the island of Mindanao as they attempt to fight the Japanese and destroy radio stations broadcasting Japanese propaganda. Making a brave push, the small band captures a former plantation that had fallen to the Japanese and been used as a shortwave broadcasting base. Logan is killed, leaving the idealistic Jeff Bailey in charge. The de facto leader is Lucky Matthews, an embittered, misogynistic engineer who has been fighting for various causes for years with his Irish pal, Tim O'Rourke. Although Lucky wants to use the captured machine guns to blast their way to the coast and possible rescue, Jeff insists that they hold the plantation and repair the generator in order to broadcast their own propaganda. After the Japanese blow up the local water supply, the guerrillas are surprised by the arrival of Wayne Ralston, a nearby plantation owner seeking shelter. With him is Edna "Eddie" Fraser, a former dancer now stuck in the Philippines and willing to marry the rich Ralston in order to forget her hard life. Lucky is irritated by the appearance of the civilians, especially Eddie, but becomes distracted when Watson, one of his men, is shot by a sniper. While Eddie tends to Watson, Ralston's selfishness become apparent as he complains about the dying man receiving a share of their decreasing water supply. Soon after, the Japanese send a warning in the form of two mutilated Moro soldiers, and once again, Eddie acts as nurse while Ralston raves about leaving. That night, when guerrilla Fillmore sneaks down the hill to get water from a well, Lucky is forced to go after him. Snipers shoot at them, but O'Rourke draws their fire, thereby saving their lives at the cost of his own. When they reach camp, Fillmore collapses, for the water was poisoned, and as O'Rourke dies, he tells Eddie to stick by Lucky even though he may treat her badly because he was once betrayed by a woman. Jeff and Gilman, a gentle member of the group, finish repairing the generator, but Ralston attempts to blow it up so that there will be no reason to remain. Corbett catches Ralston setting the dynamite and is stabbed to death by him. When Lucky and Jeff discover Ralston's act, Jeff orders Lucky to execute him. The Japanese then attack the plantation house, and Gillman is killed, and Jeff is wounded. Jeff tells Lucky that the generator is still working, and Lucky, finally convinced that Jeff is right, agrees to do the broadcasting. Before he begins, he and Santoro, a former pilot, load Jeff onto a captured Japanese plane, which Santoro has repaired and will use to fly Jeff to safety. Lucky insists that Eddie go along, but after she forces him to admit that he loves her, she returns to the house, where she tells him that everything she wants is there. As Japanese bombs fall around them, killing Heller and Armando, the last remaining members of the group, Eddie embraces Lucky and he begins the shortwave radio broadcast. He tells the Filipino and American listeners not to give up hope, to work together and remember that until MacArthur returns, the guerrillas will continue fighting. Eddie then holds Lucky tighter as he continues to broadcast and the bombing grows heavier.