In Tokyo, Japan, American diplomatic attaché Richard Saunders and his wife Mary await their seven-year-old son, Tony, who is flying to meet them. While Mary, who has learned that Dick had an affair at his last post, informs her husband that she is planning to leave him, Tony’s plane experiences engine failure and plunges into the ocean. By morning, Dick and Mary are frantic with worry, and the American embassy sends Col. Hargrave to keep them updated on the rescue operation. After fifteen hours, the first record of survivors is released, but when Tony’s name is not among them, Hargrave reluctantly reveals that a heavy fog over the ocean is making the rescue difficult. Meanwhile, while sailing off the Japanese coast, fisherrman Kei Tanaka and his wife Michiko spot an unconscious Tony floating in a life raft, and pull him onboard. They nurse him back to health, aided by their young son Asahiko, nicknamed Hiko, who speaks halting English. Soon, Hiko teaches Tony to use chopsticks, while Tony teaches Hiko to play with a yo-yo. Once they reach the Tanakas' village, however, Hiko overhears his parents discussing the imminent arrival of the police, and wrongly assuming that Tony is in trouble, runs away with his new friend. When the Saunderses learn of Tony’s rescue, they race to the village, only to find that both boys have disappeared. Although Mary and Michiko cannot converse, they feel connected in their mutual concern for their sons. The two boys hop on a truck, hoping to reach Tokyo, which Hiko vaguely knows is “over the mountains.” When the truck gets a flat tire, they find a nearby farmhouse, where the kind residents feed them. They sleep in the barn, and are at first frightened by the dark but finally fall asleep in each other’s arms. In the morning, they illegally board a train and talk about why their eyes have different shapes. Meanwhile, Mary grows more anxious, but after the farmers report having seen the boys, Japanese policeman Capt. Hibino publishes Tony’s photograph in all of the country’s newspapers and vows that they will be found soon. The children jump off the train in Kyoto and spend the day wandering past temples and through the marketplace. They dodge the police by slipping into a burlesque theater, where they worry that the women may be cold without their clothes. That night, the boys are welcomed into a geisha house, but after Hiko overhears the head geisha plan to call the police, the boys slip out at dawn. To avoid the increased police activity, they board a school bus, and there meet pretty schoolgirl Dekko, who agrees to hide them. After the teacher leads the children on a tour of important temples, they share Dekko’s lunch. By the end of the day, however, the other children see Tony’s photograph in the paper and inform the teacher. He calls the police, who notify the Saunderses and Hibino. As Hibino orders a search of Kyoto, however, the frightened boys hop on another train. There, an American G.I. buys them ice cream, but when he sees the newspaper story about the missing boys, calls the embassy. Hibino sets up a roadblock at Nara, the end of the train line, but the children escape into the city. Chased by the police, they climb several flights of stairs at a pagoda, stopping only when they have scrambled out onto the slanted roof and are perched high above the street. The Saunderses arrive as a crowd gathers below, and Dick races up to save the boys. Aided by the police, he crawls onto the ledge and pulls the boys to safety. Dick carries Tony to Mary’s waiting arms, and while looking into Dick’s eyes,she promises the boy that no one will separate the family again. When Dick turns to Hiko, however, the still-frightened boy runs away, and Dick catches him once again. Soon, everyone gathers at the Tanakas', where Dekko arrives to reunite with her new friends.