end of his final regeneration. Goth went along with his schemes mainly for power: he knew the President had no intention of naming him as a successor, but if a new election was held, Goth would be the front-runner. Before he dies, Goth warns that the Master has a doomsday plan. Attempting to piece together what the Master and Goth were planning, the Doctor inquires as to what becoming the President entails. He is told that the President has access to the symbols of office: the Sash and Great Key of Rassilon. As Engin plays records that describe how Rassilon found the Eye of Harmony within the "black void," the Doctor realises these objects are not merely ceremonial. He also realises that the Master injected himself with a neural inhibitor that mimics a deathlike state and is still alive. The Doctor, Spandrell, and Engin arrive at the morgue to find that the Master has revived. The Master seizes the Sash from the President's corpse and traps the three in the morgue. The Doctor explains that the Eye is actually the nucleus of a black hole, an inexhaustible energy source that Rassilon captured to power Gallifrey; the Sash and Key are its control devices. The Doctor deduces that the Master was planning to steal this energy to gain a new cycle of regenerations; however, if the Eye is disrupted, Gallifrey will be destroyed and a hundred other worlds will be consumed in a chain reaction. Inside the Panopticon, the Master makes his way to the obelisk containing the Eye. He unhooks the coils that connect it to Gallifrey and is prepared to access the energy. The Doctor makes his way to the Panopticon via a service shaft. The Citadel begins to quake, and cracks appear in the floor. The Doctor and the Master fight, until the Master loses his footing and falls into a chasm. The Doctor reconnects the coils and saves Gallifrey, although half the city is in ruins and many lives have been lost. The Doctor is now free to return to his TARDIS. He bids farewell but also warns that the Master may not be dead as he had harvested energy from the obelisk before he was stopped and may have been able to channel it. As the Doctor's TARDIS dematerialises, Spandrell and Engin witness the Master sneak into his own TARDIS and escape. Production Following Elisabeth Sladen's