As the conflict between Gallifrey and Skaro rages, the Cybermen are gone from the universe. Until now. The War Doctor finds himself on a world ravaged by battle, where soldiers are kept alive by grimly familiar methods. As time is manipulated, the dead no longer stay dead, and a horrifying evolution begins... Seeking answers across multiple worlds, and in a long-dead Cyber-tomb, the Doctor uncovers the terrible truth. The ultimate Cyber-form is coming to join the Time War.