The work, a social denunciation of agrarian exploitation, describes life in a small isolated Castilian village, along with the wretched existence of its inhabitants.

He lives alone with his father, Tío Ratero (Uncle Ratter - so called because he hunts water rats for food), in a cave far from the village.

His mother - step-sister to his father - was committed to a psychiatric hospital when El Nini was very young, and the boy's only emotional support now resides in the company of his dog and in his love and knowledge of the surrounding countryside.

Under pressure from the civil Governor, the mayor of the village wants to put an end to the caves, but Uncle Ratter refuses to leave the only dwelling he has ever known.

But tragedy comes when a young man from a nearby village starts hunting rats for fun in the same territory as Uncle Ratter, and prey becomes scarce.