In the third and final part of the Stormborn trilogy, the animals of the north face worsening weather in Autumn and the first stirrings of winter. With the change in conditions, grey seals and reindeer turn their attention to mating. Hormones run wild as males compete for the right to breed and young animals venture away from their parents for the first time. In Iceland, the arctic fox family at the cliff den are thriving, having fed well over the summer.  But it's a different story for the foxes denning at the shore line.  Only one out of the six cubs has survived.  Abandoned by her parents, she now has to fend for herself. On the Monach Isles in Scotland, 35,000 grey seals arrive for their annual breeding season.  A little female pup faces many dangers on the beach, including getting lost and being swept up into a fight between two raging bulls. As winter arrives, the reindeer herd in Norway must migrate from the lowlands to their grazing grounds in the mountains but this involves a perilous two-mile swim across open water.