Return of the Ice is set in Europe, 5,000,000 years into the future. The episode focuses on three species:- Shagrat - a descendant of the marmot that has grown in size and developed thicker fur to protect it from the cold. Snowstalker - a descendant of the wolverine that has evolved sabre-teeth and white fur for camouflage. Gannetwhale - a descendant of the gannet which has grown to immense size to replace the sea mammals. The episode follows the story of a female Snowstalker teaching her cubs to hunt, the Gannetwhale's breeding season and the mass migration to the south of the Shagrats.