El Mudo (the Mute) lives on the outskirts of a strange town in northern Argentina, with his dog India. Years ago he arrived from the city and moved into a mysterious house in the mountains, next to the river Tragadero. He tries to avoid everyone apart from Insúa, the owner of the general store, who tells him stories about the river and teaches him to survive by hunting monkeys. He wants simply to live alone, and for that reason he resents the interference of an elusive local who denounces him to the Fundación Vida Silvestre (The Wildlife Foundation). The arrival of a young female ecologist from the Foundation complicates life even more. In the midst of a hostile natural environment, among birds, monkeys and caimans, the reader observes with growing tension the dangers of the river and the threat from unknown parties, whose true intentions become troublingly clear to us through the eyes of the Mute.