The First, Second and Third Doctors are being pulled from time, causing the Fifth Doctor to feel himself fading from existence. They are all drawn together in the forbidden Death Zone on Gallifrey along with their companions from throughout time, but the Fourth Doctor is trapped in a time vortex, saving the Fifth Doctor’s life and giving the Doctors time to journey towards the Dark Tower at the heart of the Death Zone as they all discover that they are embroiled in the Game of Rassilon, whose prize is immortality itself.