The film opens with the wildlife of the region of Tierra del Fuego conveying the beauty and diversity inherent in a landscape that appears at first sight so uninviting. Guanacos, Andean wolves, tuco-tucos condors, crested caracaras, parrots, great crested grebes and herons are presented with their interactions. The ecology was already changed when Tierra del Fuego was settled by Europeans. But when beavers were introduced to create a fur industry, the balance was disturbed even more.
During the film it becomes increasingly apparent that a natural habitat that was once monotonous in many ways has become considerably more varied as a result of the beaver's activities. And this isn't all - new management techniques of the grandson reveal surprising results. Improved computerised bookkeeping, introduced despite the old man's objections, indicates that the valleys with beavers have significantly higher productivity rates than the "uncontaminated" valleys! When rivers are dammed by the beavers this leads to an increased accumulation of sediments. The nutrients they include finally create better pasture land. The family saga, told with an affectionate smile and great understanding for "both sides" in the duel, ends with the realisation that the beaver has also established a place for itself in the new reality of Terra del Fuego.
The film establishes a gentle, almost light-hearted narrative mode. By alternating between the perspective of the settlers and that of the beavers, the ecological relationships can be examined in a graphic and entertaining manner. The proud, temperamental gaucho constantly reacts with spontaneous affront to the activities of the beaver, who is "challenging" his domination of the land. Animosity with his Chilean neighbours emphasises this reaction: minor incidents of friction at the border (including expressions of the inevitable football rivalry) are associated with the effect of the beaver. So when a tree falls and damages the border fence, it leads to complications.