The Caves of Androzani - Plot

Plot

The dangerous desert planet Androzani Minor is the only source for a powerful drug called spectrox created by bats that inhabit the planet's caves. Spectrox is highly valued by the population of nearby Androzani Major due to its capacity to extend one's life. The spectrox mining interests are controlled by Trau Morgus, a business conglomerate leader on Androzani Major, but the operation has been threatened by the masked Sharaz Jek and his army of androids, causing public tension on Androzani Major due to limited supplies. Morgus has publicly funded a military operation by the Androzani Major's government against Jek's androids, but at the same time has secretly backed a gunrunning group to deliver weapons to Jek to profit from the war.

The TARDIS lands on Androzani Minor, and the Doctor and Peri decide to explore a set of tracks that lead into a nearby cave. As they explore, they are briefly caught in a ball of an unknown sticky substance, but they easily break free. Further into the caves, they discover a hoard of weapons, but are then captured by General Chellak's forces, believing the two to be working for gunrunners Stotz and Krepler. Morgus orders their execution after seeing that Chellak's "gunrunners" are not his own men over holographic communication. When the two are brought to the execution squad, they are found to be androids, as the Doctor and Peri have since been rescued by Jek who had been watching the two enter the caves and was able to prepare duplicate androids with help of his personal android Salateen.

At Jek's base, the two complain about rashes and cramps in their bodies where they touched the sticky substances, Salateen (also a prisoner) realises they have been subjected to the first stages of spectrox toxemia from exposure to unrefined spectrox, and that while there is an anti-toxin, it requires the milk of the queen bat. Unfortunately, due to the mining activity, all the bats have migrated to deeper levels of the caves where there is no oxygen. Before leaving to meet with the gunrunners while leaving the two under his androids' guard, Jek explains that he is seeking revenge against Morgus as it was his actions that left his face disfigured. After Jek leaves, the Doctor is able to reprogram the androids and allows for him and Peri to escape, but they quickly encounter Chellak's forces; Peri is recaptured while the Doctor is caught by Stotz. Stotz decides to take the Doctor back to Androzani Major to see Morgus directly. As Stotz discusses the situation with Morgus via holographic communication en route, Morgus sees the Doctor still alive, and fearing deception, kills the President of Androzani Major and makes his own plans to travel to Androzani Minor to put the situation right himself. The Doctor is able to gain control of the ship from Stotz and crashes it back on the surface of Androzani Minor; weary from the spectrox poisoning, he makes his way into the caves to try to save Peri.

Meanwhile, Chellak plans an assault on Jek's base, luring him to believe an attack lies elsewhere. The battle kills nearly all of the military forces including Chellak, the gunruners, and Jek's androids; Jek is able to rescue the unconscious Peri from the military base and return her to his base amid the chaos. The Doctor arrives, struggling to hold off his body's attempt to regenerate to rid itself of the spectrox. Jek provides him with a limited air supply and equipment and directions to find and milk the queen bat. As the Doctor departs to get the milk, Morgus arrives on the planet, finding that his shrewd secretary has deposed him from power. Morgus quickly deals with Stotz to kill all the remaining gunrunners, including Krepler, and then plot to secure Jek's private stash of spectrox so they may disappear quietly to another planet. The two make their way to Jek's base, lured by fans that Jek is using to try to keep the base temperature cool for Peri. A brief fight breaks out, and Jek, Morgus, and Stotz are killed. The Doctor arrives just after the battle and takes Peri back to the TARDIS on the surface as the planet erupts around them. While unlocking the TARDIS, the Doctor accidentally spills some of the bat's milk.

Inside the TARDIS, the Doctor gives Peri the remaining bat's milk and collapses. Peri quickly recovers and finds him lying in pain on the floor. The Doctor explains that there was only enough bat's milk left to cure her, but his body will shortly regenerate, though it feels different from his previous regenerations. The Doctor begins to hallucinate images of his past Companions urging him to continue to fight for his life, followed by The Master laughing at his state. The Doctor says 'Adric' before the regeneration completes, with the Doctor suddenly alert and active though with a new face. When Peri asks what is happening, the Doctor replies, "Change, my dear, and it seems not a moment too soon..."