With their father dead and no food to keep the family through the hard winter, an Inuit brother and sister set off to retrieve a caribou their grandfather shot and buried months before, when he was too weak to haul it the three days' distance to their home. For the journey, the grandfather makes Pitokak and Upik sled runhers of frozen caribou skins and cross bars of their last three frozen fish. On the way, a storm keeps them holed up for three days in their overnight igloo, and on the return trip, hauling the caribou, their endurance is tried. But the chief obstacle is a large grizzly who follows them home, getting closer and closer though they throw him the runners and fish to gain time. Finally, is a desperate confrontation just outside their home, the stronger Pitokak collapses from hauling the carcass on his back, and his sister Upik, previously the less brave, places herself between him and the bear and finally sends the animal ambling off with the last of the fish. The only explanation we have for the bear's odd loss of interest in the carcass is grandfather's ""No human being knows exactly what the animals will do."" Grandfather also has the last word on Upik's performance: ""Nobody knows the strength or courage that humans possess until real danger comes to test them."" Houston's demonstration of this truth--or truism--is neither subtle nor even as forceful as some of his earlier adventures, but the realities of Arctic hardship and endurance give the story some predictable strength.