The film begins at an outpost with Tweed expecting to leave Guam to go back to mainland America. His replacement, Roy, arrives along with Vicente, a local. Shortly after the bombing of Pearl Harbor, the Japanese launch an air attack on Guam, and the resulting chaos kills both Vicente and Chief Schultz. The five remaining men run for the hills.
Meanwhile, the Japanese have obtained medical documents from the American prisoners and have discovered that five men are missing. The five escape an oncoming Japanese patrol with the help of a local man and his son. However, their escape is short lived. While crossing a swamp, Roy loses a shoe and then steps on a scorpion. While not killing him, the toxins make him too weak to walk, forcing the men to stay put. As another Japanese patrol comes, the men decide to hide Roy with some brush, and Tweed gives him a pistol, promising him that he'll "be back for the gun". However, rather than running away, Turney decides to try to convince Roy to surrender with him, saying that the Japanese will take care of Roy's foot and that no harm can come to them because they will be prisoners of war. Turney uses his white shirt to signal to the Japanese his surrender. However, he is promptly killed. Panicking, Roy kills a Japanese soldier with the pistol, but he is shortly thereafter killed by a grenade.
The three remaining men then stumble upon a copra plantation, where they meet Sus Quintagua, who promises to take them to his boss Santos, saying that he will know where they can hide. However, a plan to smuggle the Americans past the Japanese goes wrong when Chico is killed by a stray shot by a drunken Japanese officer into one of the carts. The officer lets the rest of the copra convoy go without searching it in exchange for Quintagua's bottle of coconut wine. Quintagua reveals that he has hidden an old radio, and the two Americans try to fix it. However, the battery runs out, and so, without Tweed knowing, Quintagua and Sonnenberg travel back to their abandoned jeep to get its battery. The Japanese then arrive at the village where Tweed is hiding. Tweed takes the radio with him, and Quintagua's wife shows him the way away from the village. They come upon the bound and beheaded bodies of Sonnenberg and Quintagua.
Tweed then makes it to a leprosy hospital, where he is taken care of by a priest and his assistant. Tweed is told that the Japanese would not dare come there, so he will be completely safe. The hospital even has a functioning radio, and Tweed decides to use a typewriter to write what he hears on the radio onto a makeshift newspaper called the Guam Eagle, which is secretly passed among the locals. However, the plan goes awry when the newspaper, meant to be read and then burned, incites the locals to rebel against the Japanese. The Japanese learn of the Guam Eagle. Shimoda reads one of the papers, and quickly sniffs out medicine, leading them to believe that Tweed is hiding in the leprosy hospital. The Japanese arrive at the hospital, gathering up all of the villagers. Tweed hides with the lepers in the isolation ward, as the Japanese soldiers are too horrified by the patients to look for him in there. However, a small fire is accidentally kicked into a house, causing it to catch on fire. Despite the people's efforts to put it out, the hospital is burned down. The priest is suspected of being the one who distributed the newspaper, and is taken away to be questioned.
Tweed then awakes to find the priest's assistant and a man named Antonio Cruz. Fearing for his family's lives because the Japanese have declared anyone found helping Tweed will be executed, Antonio hides Tweed at the top of a large formidable rock face with a cave at the top. Antonio promises to bring supplies every now and then. Tweed then meets Antonio's beautiful daughter Josephina, or "Joe", who brings supplies in her father's stead. A nearby Japanese patrol is alerted to their position by an alarm clock that Joe brought with her. However, Tweed converts the alarm clock into an alarm that signals if anyone has found his location. The Japanese then pass another declaration stating that after one month, a farm in each district will be burned down if Tweed is not surrendered, dead or alive. Tweed, overcome with guilt, decides to turn himself in, but is stopped by the assistant and Antonio. The two men take Tweed's dog-tags, stating that they will "give him dead". Under the cover of night, the locals take the body of the recently deceased Shimoda and take it to the sea, where the flesh is eaten by crabs, leaving only a skeleton with Tweed's dog-tags on it.
Antonio's family comes to celebrate Christmas with Tweed, and Antonio reveals that the Japanese have left Guam, save a few in Agana. Tweed is then surprised by a visit from the newly released priest and his assistant. However, they soon discover that the Japanese military is building up its forces and preparing for an attack by the US. Tweed discovers a Japanese gun position and, using a mirror, manages to warn an American ship away from the Japanese cannons. Tweed asks Joe not to come back because he fears it is too dangerous. The two share a passionate embrace and reluctantly part. Later that night, the American ship signals back to Tweed, but it alerts the Japanese to his position. Tweed signals that he has vital information. Tweed manages to rendezvous with the ship; his Japanese pursuers are killed.
After the battle ends with an American victory, Tweed re-unites with Antonio and his family, hugging Joe on top of the rock where Tweed hid.