Hidden beneath the Arctic snow a mother polar bear proudly gives birth to two cubs named Nanook and Stella. Knowing only of the cave and snow, these two siblings soon desire to explore the dangerous world above. Their mother Ursula does not permit them to leave while the two are still young and weak, but while their mother sleeps Stella convinces her brother Nanook to help her get a look outside.
The siblings are amazed at the size of the snowy world around them and are worried about getting lost, but Nanook becomes interested in an arctic fox and runs away. A panicked Stella believes that her brother will be eaten and runs to their mother for help, but before the misunderstanding can be cleared they are all sent running by a flood of water. Ursula is forced to watch as their home is washed away, leaving the three of them stranded in the harsh winter land.