Death to the Daleks is the third serial of the 11th season of the British science fiction television series Doctor Who, which was first broadcast in four weekly parts on BBC1 from 23 February to 16 March 1974.
In the serial, the Daleks and a human expedition both arrive on the planet Exxilon to seek a mineral found in abundance there. This was the last serial to have an episode's master tape wiped, but all episodes now exist in colour in the archives.
Plot
The TARDIS suffers an energy drain and lands on the planet Exxilon. The Third Doctor and Sarah Jane Smith go to investigate the cause of the interference, and become separated. The Doctor is captured by the planet's inhabitants, the savage Exxilons, but escapes. Sarah Jane is attacked by one of the creatures in the TARDIS, and flees, finding a huge city with a flashing beacon.
At dawn, the Doctor is found by a party of humans from the Marine Space Corps; they take him to their ship, which has been stranded by the power drain. They are on an expedition to mine "Parrinium" – a mineral abundant only on Exxilon – which can cure and give immunity from a deadly space plague. If the expedition does not leave the planet with a supply of Parrinium within a month then millions will die. They show the Doctor photos of the nearby city – which the Exxilons worship, sacrificing anyone who ventures too close. Sarah Jane does so and is captured and taken to the Exxilons' caves to be sacrificed by their High Priest.
Another ship arrives, and four Daleks emerge. Their ship has also been affected by the energy drain. The Daleks encounter the Doctor and attempt to exterminate him, but their weapons do not work either. The Daleks claim that several of their planetary colonies are suffering from plague; thus they need Parrinium for the same reason as the humans. The Daleks, the Doctor, and the humans form an uneasy alliance to obtain Parrinium and escape Exxilon. While the allies are making their way to the humans' mining dome, the Exxilons ambush them. A battle ensues and the Exxilons end up killing a human and a Dalek and capturing the others. The prisoners are taken to the Exxilon caves where the Doctor interrupts Sarah Jane's sacrifice; therefore, he is also condemned to death. When the dual sacrifice commences, a second party of Daleks arrive, which have replaced their energy weapons with mechanical firearms that use bullets. The Daleks kill a number of Exxilons, then force the Exxilons and humans to mine Parrinium. The Doctor and Sarah Jane flee into tunnels. The other party of Daleks arrive and they discuss their actual plan to use Parrinium to create a plague and spread it across every planet except their own.
The Doctor and Sarah Jane meet a group of subterranean, fugitive Exxilons. Their leader, Bellal, explains that the city was built by the Exxilons' ancestors, who were once capable of space travel. They built the city to be capable of maintaining, repairing, and protecting itself. Fitting the structure with a brain meant that the city no longer needed its creators. On realising this, the Exxilons had tried to destroy the city, but the city destroyed most of them; the savage surface dwellers and Bellal's group are the only survivors. Bellal's people seek to complete their ancestors' last, failed act – to destroy the city and ensure their race's survival. Bellal sketches some of the markings on the city wall; the Doctor recognises the markings from a temple in Peru deducing that the ancient Exxilons visited Earth. Bellal also explains that the city supports itself through underground "roots" and the aerial beacon. The Doctor realises that the beacon must be the cause of the energy drain and decides to go to the city and resolve the problem.