The story takes place in China during World War II as Japan is invading. Tien Pao's home is a sampan, a flat-bottomed houseboat, in which he and his family escape on the river when the Japanese overtake his village, The-Corner-of-theMountains-Where-the-Rivers-Meet. The family goes to Hengyang, where the mother and father can find work at an American airbase while living in their sampan.

During Tien Pao's journey from enemy-occupied territory back to Hengyang, he spends a great deal of time in the Chinese countryside, guiding himself through the mountains by following the river. The mountainous terrain provides Tien Pao with places to rest and hide but not with food. It is a dangerous place for the boy and his pet pig because Japanese soldiers are also on their way to Hengyang.

The American airbase, full of friendly soldiers, and the nearby town of Hengyang, alive with desperate people fleeing...