They head for their traditional breeding ground where – after a ritual courtship of intricate dances and delicate maneuvering, accompanied by a cacophony of ecstatic song – they will pair off into monogamous couples and mate. The females remain long enough only to lay a single egg. The males are left behind to guard and hatch the precious eggs, which they cradle at all times on top of their feet. Subjected to subzero temperatures and the terrible trials of the polar winter, they face great dangers.

After two months during which the males eat nothing, the eggs begin to hatch. The chicks can not survive for long on their fathers’ limited food reserves. If their mothers are late returning from the ocean with food, the newly-hatched young will die.

Once the families are reunited, the roles reverse, the mothers remaining with their new young while their mates head, exhausted and starved, for the sea, and food. As the weather grows warmer and the ice floes crack and melt, the adults march many hundreds of miles over some of the most treacherous territory on Earth, until the chicks are ready to take their first faltering dive into the deep blue waters of the Antarctic.

Nanu and Seela might be rivals in the wild, but together they now face a single danger. Both must seek out new ways to live in a world where the rules have changed. The tale begins as Nanu, a fluffy polar bear cub, bursts with her mother and brother from their winter den on Snow Mountain, scampering, tumbling and sliding through the heavy snow with joyful abandon. At the same time, Seela, an endearing walrus pup, emerges into the world, joining her close-knit family herd on the icy islands of the surrounding sea, where they sun, snuggle, scratch, snooze and emit a symphony of blissful grunts and groans.