Earth is in the grip of a new Ice Age, and the Doctor arrives at a station tasked with keeping the ice at bay using an ioniser. As the glacier moves forwards, a frozen creature is dug out of the ice - a reptilian-looking humanoid jokingly termed an "Ice Warrior" by the base personnel. The Ice Warrior thaws and wakes up, stating his name is Varga and it was the commander of a ship from "the Red Planet" which crashed on Earth thousands of years ago. Now that his own planet is dead, Varga plans to conquer earth with the help of his similarly-frozen comrades.