The Doctor and Ace arrive in Shoreditch in 1963 and become quickly ingratiated with Professor Jenson and Sergeant Mike Smith who are tracing 'the primary source' of magnetic fluctuations outside Coal Hill School. They are quickly summoned to 'the secondary source' at Totters Lane Junkyard where Group Captain Gilmore and his men have been attacked by an unidentified assailant. The aggressor is quickly identified as a grey Dalek which is promptly destroyed by the Doctor using Ace's Nitro-9 explosive.
Meanwhile, Gilmore's troops, charged with returning the grey Dalek remains, are attacked by agents of Mr. Ratcliffe, whose fascist Association operates from a Builders Warehouse. His agents recover the remains which Ratcliffe presents to a Dalek Battle computer secreted in his office whom he assures that the Doctor will be followed.
The Doctor, troubled by the presence of the 'wrong Dalek', travels with Ace back to Coal Hill School, and with the permission of the Headmaster begin searching the school. The Doctor reveals to Ace that the Daleks have followed him through time to this point hoping to secure the Hand of Omega.
In the basement of the school the Doctor and Ace discover a transmat device which the Doctor disables, causing a white and gold Dalek operator to charge on the saboteurs. While Ace is incapacitated by the controlled Headmaster, the Doctor is locked in the cellar to face the rising Dalek chanting his extermination. Ace overpowers the Headmaster and frees the Doctor, and they make use of anti tank rockets forwarded by Group Captain Gilmore to deal with the Dalek.
Very concerned about the presence of two Dalek factions, the Doctor decides to 'bury the past' and leaves Ace in the care of Smith. The Omega Device is awaiting burial in a local Undertakers. The Doctor leads the floating casket to a freshly dug grave. As the blind Vicar presiding over the ceremony announces 'it is over' the Doctor corrects him with 'it's only just beginning.' The unusual burial is watched by Mike Smith.
The Doctor, Smith, Jensen, and her assistant Allison travel to Gilmore's base where the presence of a large Dalek mothership is detected in geostationary orbit. The mothership quickly dispatches an Imperial Dalek assault squad to the transmat repaired by the Headmaster. The Doctor vetoes a proposal of military action, warning of massive reprisals from the Imperial Faction. He assembles a jamming device to interfere with the Dalek control systems.
A bored Ace realises that she has left her stereo back at the school. She returns there to discover it crawling with Imperial Daleks. With some assistance from a baseball bat imbued with power from the Omega Device she proves more than a match for a surprised Dalek scout. However during her escape she is cornered by three Daleks.
Alerted to Ace's visit to the School, the Doctor arrives just in time to save Ace using his Dalek Jammer. Deciding to buy himself more time he then destroys the transmat. The Daleks on the Mothership detect this and decide to wait for the Omega Device to reveal itself. Informed of the location of the buried casket and the Battle Computer's promise of great shared power, Ratcliffe and his association begin digging for the Device. He is unsettled by the presence of a silent school girl who has been observing most of the proceedings. The disturbed Device is detected by the Imperial Daleks and the summoned Dalek Emperor tasks a shuttle to recover it from the Grey Renegade Daleks who have rejected his authority.
The Doctor sends Gilmore and his men to establish a defensive position at the school. He reveals to Ace that two sets of Daleks are vying for control of the Omega Device which was used to give the Gallifreyans mastery of time. Ratcliffe presents the Device to the Battle Computer which is revealed to contain the little girl. A Dalek Supreme flanked by Grey Daleks kills Ratcliffe's men and takes him hostage. They quickly prepare to flee with the Device using a time controller (visually represented by a plasma lamp).
Not wanting this faction to escape with the Device, the Doctor disables the controller and is chased back to the school by a squad of Daleks. The Doctor asssures his entourage that the approaching Imperial shuttle will not land at the school as it is so far away from the Renegade base. The group take cover as the shuttle lands in the playground. The Doctor notes with concern that he might have miscalculated.
The Imperial Daleks leave the ship to face the Renegade faction. Using a Special Weapons Dalek to neutralise some opposition, they advance towards the Renegade base. Realising that Smith is Ratcliffe's agent, Gilmore detains him. The Doctor decides to use the transmat remains in the cellar as a communications link with the Mothership.
Smith escapes to the Renegade base to find Ratcliffe a prisoner. The repaired time controller powers up to enable the Renegades' escape but the base is attacked by the Imperials, who overwhelm the few remaining opponents. Ratcliffe and Mike flee with the Time Controller and the Supreme Dalek orders the controlled girl to recover it. Using Dalek powers she kills Ratcliffe and pursues Smith. The victorious Imperials return to the shuttle with the Device. The Doctor orders Ace to shadow Smith.
The Imperial Emperor is informed that the Omega Device is in his possession. Soon after the face of the Doctor appears on the bridge screen and he demands the surrender of the Device. The Emperor is revealed to be Davros who announces his plans for his Daleks to overthrow the Time Lords. Angered by the Doctor's insults, Davros decides to unleash the device on Skaro's sun. Rather than the desired effect, the device creates a supernova, obliterating the Daleks' home. The device smashes back into the Mothership just after Davros' escape pod tumbles out of view. The Doctor announces that the device is travelling back to Gallifrey.
Ace is captured by Smith, who is still holding the Time Controller. The girl tracks him down and kills him before turning her attention to Ace. The Doctor seeks out the Supreme Dalek. Convinced of its absolute defeat it kills itself, breaking the link with the controlled girl.
At Smith's funeral Ace wonders if what they did was good. 'Time will tell,' replies the Doctor. 'It always does.'
Doctor Sylvester McCoy (Seventh Doctor)
Companion Sophie Aldred (Ace)
Terry Molloy — The Emperor Dalek/Davros
Simon Williams — Group Captain Gilmore
Pamela Salem — Dr Rachel Jensen
Karen Gledhill — Allison
Dursley McLinden — Sgt. Mike Smith
George Sewell — Ratcliffe
Harry Fowler — Harry
Jasmine Breaks — The Girl
Joseph Marcell — John
Peter Hamilton Dyer — Embery
Michael Sheard — Headmaster
Peter Halliday — Vicar
William Thomas — Martin
Derek Keller — Kaufman
John Leeson — Voice
Hugh Spight, John Scott Martin, Tony Starr, Cy Town — Dalek Operators
Roy Skelton, Royce Mills, Brian Miller, John Leeson — Voices/Dalek Voices
Writer Ben Aaronovitch
Director Andrew Morgan
John Nathan-Turner (uncredited)
Script editor Andrew Cartmel
Producer John Nathan-Turner
Executive producer(s) None
Production code 7H
Series Season 25
Length 4 episodes, 25 minutes each
Originally broadcast October 5–October 26, 1988