S1, E5: A season of complete darkness, and the worst weather anywhere on the planet - it's midwinter in the Antarctic. The hostile landscape seems completely devoid of life, but under the ice life still abounds. Ghost-like white fish are kept alive by anti-freeze in their blood and giant seaspiders patrol the sea bed. While in the centre of the continent, male Emperor penguins huddle for warmth throughout the winter, each incubating a single egg.