The Marañón River is born in the highlands of Peru and it flows across large areas of the Peruvian territory and through the life of a peasant family that dwells upriver, over four thousand meters high. It runs into the warm lands of the Inter-Andean valley, where a 13-year-old girl exposes herself to risk by selling fruit to truck drivers, and through the Amazon rainforest, where indigenous Awajun children make competitions to prove their knowledge. It eventually arrives at the mouth, the workplace of a river merchant. The core theme of the four stories brought together in the documentary is the challenge of surviving amidst isolation in remote regions bathed by the waters of the Marañón River.