The Doctor, following the preceding events of The Armageddon Factor, has installed a "Randomiser" onto the TARDIS, to elude the Black Guardian, and is repairing K-9. Meanwhile, Romana regenerates into the form of Princess Astra from the preceding adventure, in spite of the Doctor's disapproval. The TARDIS then lands...
The TARDIS has landed on a seemingly very rocky planet which has breathable air and hospitable conditions; but has dangerously high levels of radioactivity. He gives her tablets to combat the radiation and a beeper-like device to inform her when she must take her pills. They exit the TARDIS and establish that this a rocky planet with seismic disturbances. They witness what appear to be ragged-looking natives burying one of their dead (although this deceased fellow is not all he appears: he is from the planet Kantra, a tropical paradise; so he should not have been there in theory). They come across a spaceship which half-buries itself into the ground in a valley; and just as the Doctor and Romana are about to investigate, underground explosions force them back towards the ruins. Whilst exploring the ruins, another underground explosion occurs, causing a column to fall on the Doctor. Romana attempts to lift the column on her own, but it is too heavy for her. She agrees to return to the TARDIS to reassemble the literally "brainless" K-9 and get him to assist in removing the debris. She sets off, but finds the TARDIS half-buried in rubble (and, unbeknownst to her, she is being followed). Realising that she cannot reach K-9, she starts to turn back.
Meanwhile, the Doctor is quite happily reading a book ("Origins of the Universe" by Oolon Colluphid), and remarking that he needs to remind Romana to take her anti-radiation pills, a troupe of silver-haired humanoids appear and point their weapons at him. He seems to try to charm them, but it does not seem to be working.
Romana returns to the ruin, to find that the Doctor has vanished. As she turns to leave, she finds the man who has been following her blocking her path. She backs away, only to fall down a rubble chute, and she loses consciousness. The man then prepares to climb down and help her, but before he can do so she recovers consciousness and hears a noise coming from one of the walls that resembles drilling. She backs away from the wall; when suddenly a pair of Daleks burst through the wall: "Do not move. Do not move. Do not move! Do not move! Do not move! Do not move! You are our prisoner - do not move! You are our prisoner!"
The Daleks threaten to exterminate Romana if she does not comply with their instructions explicitly, and then command Romana to come with them. (The man, meanwhile, has seen the whole thing.)
Meanwhile, the Doctor is thanking the Movellans (as these silver-haired humanoids are called) for helping him, and he remarks at their strength. He then asks their commander, Sharrel, where he is, and Sharrel replies that the planet is known as D-5-Gamma-Z-Alpha. The Doctor then states that he is rather old fashioned and enquires to its real name. He is astonished hear that they are on the planet Skaro, and that the Movellans are here to wage war against the Daleks.
Romana, meanwhile, is being interrogated by the Daleks. After they learn that she is of no threat to them, the Daleks command Romana to work at one of their drilling sites.
Back at the Movellan space craft, two Movellans enter with a new prisoner, it's the man who has been following the Doctor and Romana; he identifies himself as Starship Engineer Tyssan, who was captured by the Daleks two years ago. He collapses after revealing that the Daleks have used him during a drilling operation for a search operation. He soon comes around, and says he does not know what the Daleks are looking for. He then tells the Doctor about what has happened to Romana, and they set out to rescue her.
In the meantime Romana meets with some other workers, with whom she discusses the Daleks' hatred for humanoids, and she learns that she is getting weaker as a result of radiation sickness. She learns that the only way out is to die; when within minutes she seems to die. Her fellow workers remove her body.
The Doctor, Tyssan and the Movellans Sharrel, Lan, and Agella are shocked to find Romana's grave. As the Doctor frantically tries to dig her out, she appears and explained that she feigned death to escape, and that at school she was taught how to stop her hearts. They then head into the Dalek headquarters. Lan is left on guard outside of the Control Center, and is shot by a Dalek who is out searching for them. The Doctor establishes that the Daleks are searching for something on a level that they have yet to access. He remembers an alternative route to this area, so he, Romana, and Agella make their way to this floor while Sharrel returns to his ship. There they discover Davros, the creator and leader of the Daleks (who was seemingly exterminated at the end of Genesis of the Daleks). Something gives way up above, and part of the ceiling collapses onto Agella. Whilst the party is distracted by this, Davros starts to stir: his fingers move, his central, artificial eye lights up - and Davros lives...
The Doctor finds Davros and takes him into a blocked-off room in the old Dalek city. He lets Romana and Tyssan escape out of the window, and they return to the Movellan ship. The two geniuses talk about the Daleks' "accomplishments": whilst the Doctor comments on the countless lives the Daleks have ruined, Davros replies that this is only the beginning - the Daleks have only just begun their conquest of the cosmos. The Daleks find them both, and proceed to exterminate their prisoners until the Doctor complies. The Doctor then threatens to kill Davros with a makeshift explosive he has just concocted. He then orders the Daleks to free all their prisoners, and to let him escape. The Daleks say that these conditions are unacceptable and illogical (and therefore, to a Dalek, impossible); and that the exterminations would continue. However Davros makes them see that the Doctor's logic is "impaired by irrational sentiment". The Daleks then comply, and the Doctor attaches the explosive to Davros' chair, and tells him that it will detonate when he uses his sonic screwdriver. He then escapes. Davros frantically orders the Daleks to remove the explosive; which they do (although the Doctor detonates and the explosion seems to take a Dalek with it). Davros then vows to make the Daleks invincible, and the supreme power of the universe. (However, we notice that Agella is not dead; and that she will return and report all she has just heard to her fellow Movellans.)
Romana reaches the Movellan spaceship; but learns that the Movellans are not as altruistic as they appear; and Agella uses her weapon on her, which knocks her out. The Movellans than test out their nova device: a weapon which changes air molecules so that a planet's atmosphere becomes flammable and can be set alight - killing all lifeforms.
The Doctor meets up with Tyssan and they both find a Movellan scout. The Doctor deactivates her by removing the power pack/controlling circuit on her belt and reveals that the Movellans are, in fact, robots. He finds that the unconscious Romana has been attached to the nova device (sealed inside an airtight container). He sends Tyssan away and tries to open the container, as the timer is ticking down...
Just as the timer approaches zero, the Doctor is knocked out by one of the Movellans' weapons. However, the nova device was revealed to be a "dud" - a decoy used to lure the Doctor.
The Doctor learns that the Daleks and Movellans have been in a stalemate for over two centuries, and that both sides' battle computers have been calculating the best strategy and precise moment at which to attack - so far not a single shot has been fired. The Daleks want Davros to help them gain an advantage. The Movellans want the Doctor to do the same for them, which the Doctor refuses to do. Davros, on the other hand, is all too eager to give the Daleks the upper hand; and he orders them to make a suicide bombing attack on the Movellan craft upon realising that the Doctor might do the same thing for the Movellans. Meanwhile, Tyssan manages to gather up the prisoners and leads an attack on the Movellans, ending with them all being deactivated.
While the prisoners take control of the Movellan ship, the Doctor makes his way to the city to confront Davros. The Doctor informs Davros that the Movellans have been disabled; unfortunately Davros does not believe him and intends to destroy the Movellan ship anyway. As the Daleks approach the ship, the Doctor goes to detonate the bombs prematurely, only to discover too late that Davros didn't send all the Daleks on the suicide run when one ambushes him and holds him at gunpoint.
The slaves are no match for the Daleks, who begin exterminating them. Seeing the events, the Doctor throws his hat on the Dalek's eye-stalk, blinding it. As the Dalek fires around blindly (nearly killing Davros in the process) the Doctor attaches an explosive to it and blows it up, then activates the bomb detonator and destroys the attacking Dalek squad. He then takes Davros into the custody of the former slave workers. Davros shall be placed in cryogenic suspension and taken to Earth to stand trial for his crimes. The Doctor and Romana leave; remarking on the fact that whoever makes mistakes often wins (as the Doctor knows only too well).
Doctor Tom Baker (Fourth Doctor)
Companion Lalla Ward (Romana II)
David Gooderson — Davros
Mike Mungarvan, Cy Town — Daleks
Roy Skelton — Dalek Voices
Peter Straker — Commander Sharrel
Suzanne Danielle — Agella
Tony Osoba — Lan
Tim Barlow — Tyssan
Penny Casdagli — Jall
David Yip — Veldan
Cassandra — Movellan Guard
Writer Terry Nation
Director Ken Grieve
Script editor Douglas Adams
Producer Graham Williams
Executive producer(s) None
Production code 5J
Series Season 17
Length 4 episodes, 25 minutes each
Originally broadcast September 1–September 22, 1979