Oxygen Investigating a distress signal, the Doctor pilots the TARDIS to the Chasm Forge space station in the far future. There, he, Bill and Nardole encounter the walking dead. Time and air are running out, and every breath comes at a price. Extremis The Doctor is blind, but hides the truth from Bill. A copy of an ancient book, the Veritas, is about to go viral, but everyone who reads it kills themselves. The Pope requests that the Doctor discovers the book's secret by reading it himself...but he cannot see. The Pyramid At The End Of The World An ancient pyramid appears in a war zone. Inside are aliens who warn that the extinction of all life on Earth is imminent, but they offer salvation...at a price. The Doctor searches for the cause of the world's end, and Bill prepares to make a fateful deal.