The episode is set in North America, 5 million years into the future. The episode focusses on three species: (1) Deathgleaner, a massive carnivorous false vampire bat that spends the day hunting for prey in the desert and spends the night in a communal roost; (2) Spink, a descendant of the quail whose wings have become digging blades. The species lives much like the naked mole-rat of our time; (3) Desert Rattleback, a descendant of the agouti, when lives in the cold regions. The episode explains that the onset of the ice age caused the agricultural belt of the USA to turn into a desert where temperatures at night regularly reach freezing. The episode shows how the animals have evolved to cope with the harsh features of this forbidding landscape.