Summary: The Doctor and Ace travel to Russia during the Cold War and discover that Martian relics are being used to construct a new weapon. An Ice Warrior named Sezhyr has been resurrected. And Ace learns just what plans the Doctor had in store for her.
Summary: The Doctor and Ace return to Perivale, and Ace discovers no one remembers her and all of her friends are gone. A mysterious race of aliens that are half-cheetah, half human are attacking people. The Doctor and Ace discover that they are in league with the Master. But the Master has changed. He has become like these creatures, so savage that he is no longer himself. And the same thing happens to everyone they come in contact with.