It was the first series produced and broadcast in colour and the first set entirely in one time period and almost entirely on Earth (the latter of these factors would later be repeated for Season 26 and Series 1, although in those two cases there was no attempt at an in-universe explanation for confining the Doctor to the planet). Although the series did not have an overall story arc, it did feature a recurring subplot of the Doctor trying to adjust to life as an exile while trying to circumvent the restrictions placed upon him by the Time Lords, and began the process where the Doctor would try to gain more control over his TARDIS. Beginning with this series and continuing for the next few years, most storylines involve the Doctor working with UNIT.
Episode 1
Spearhead from Space (1)
Jan 3, 1970
As the newly-regenerated Doctor arrives on Earth, so does the Nestene too.
Episode 2
Spearhead from Space (2)
Jan 10, 1970
UNIT's attempts to locate the meteorites are hampered by the mysterious plastic Autons, being constructed by Channing at a nearby factory, while the Doctor makes another attempt to escape from the hospital.
Episode 3
Spearhead from Space (3)
Jan 17, 1970
Ransome manages to escape from the plastics factory and alert UNIT, prompting the Doctor and the Brigadier to start an investigation.
Episode 4
Spearhead from Space (4)
Jan 24, 1970
With UNIT's investigation being blocked by the Replica of Scobie, the Doctor and Liz visit Madame Tussaud's to try and find out more as Channing prepares to activate the Autons.
Episode 5
Doctor Who and the Silurians (1)
Jan 31, 1970
The Doctor and Liz are summoned to the Wenley Moor Research Centre by the Brigadier, after several staff members suffer nervous breakdowns.
Episode 6
Doctor Who and the Silurians (2)
Feb 7, 1970
The Doctor attempts to convince people there are monsters in the caves, prompting Major Baker to start shooting at a reptile man.
Episode 7
Doctor Who and the Silurians (3)
Feb 14, 1970
The Silurians contact Quinn for help in retrieving the creature while the Doctor and the Brigadier organise a search of the moors.
Episode 8
Doctor Who and the Silurians (4)
Feb 21, 1970
With Quinn dead, the Brigadier decides to take an armed party into the caves, prompting the Doctor to contact the Silurians himself.
Episode 9
Doctor Who and the Silurians (5)
Feb 28, 1970
Worried about the Old Silurian's growing friendship with the Doctor, the Young Silurian has the scientist infect Baker with a virus and then release him.
Episode 10
Doctor Who and the Silurians (6)
Mar 7, 1970
While the Doctor and Liz try to find a cure to the virus spread by Baker, the Young Silurian kills the Old Silurian and takes control of his people.
Episode 11
Doctor Who and the Silurians (7)
Mar 14, 1970
While Liz distributes the cure to the virus, the Doctor discovers the Silurians now plan to wipe out humanity by destroying the Van Allen Belt.
Episode 12
The Ambassadors of Death (1)
Mar 21, 1970
While the Brigadier investigates a loss of contact with Mars Probe 7, the Doctor realises signals coming from the probe are of extra-terrestrial origin.
Episode 13
The Ambassadors of Death (2)
Mar 28, 1970
UNIT retrieve the returned Recovery 7 but then Carrington hijacks it while the Doctor and Liz try to decode the signal he sent.
Episode 14
The Ambassadors of Death (3)
Apr 4, 1970
Carrington is holding the astronauts at a secret location but when he takes the Doctor, Liz and the Brigadier there they find they have been kidnapped.
Episode 15
The Ambassadors of Death (4)
Apr 11, 1970
Liz has been captured by Reegan's men and the Doctor begins to suspect Taltalian is more involved than he appeared.
Episode 16
The Ambassadors of Death (5)
Apr 18, 1970
The Doctor decides to take Recovery 7 back into space to search for the missing astronauts but Reegan sabotages the launch.
Episode 17
The Ambassadors of Death (6)
Apr 25, 1970
The Doctor speaks with the alien captain and learns the astronauts sent to Earth were ambassadors. However, before he can alert the authorities he is kidnapped by Reegan.
Episode 18
The Ambassadors of Death (7)
May 2, 1970
Carrington is planning to expose the aliens on live television and call for an interplanetary war and the Brigadier must rescue the Doctor and Liz in time to stop him.
Episode 19
Inferno (1)
May 9, 1970
England, the near future. UNIT is providing security and scientific support for the Stahlman project, an attempt to tap the Earth's core for energy. But things are already going wrong…
Episode 20
Inferno (2)
May 16, 1970
Strange deaths, men changing into monsters, hot green slime pouring out of the waste pipes – but Professor Stahlman is determined to press ahead with the Inferno project no matter what the cost!
Episode 21
Inferno (3)
May 23, 1970
The Doctor has vanished from the Inferno project… or has he? He finds himself in the same place, but everyone has changed… and the drilling is closer to its deadly conclusion.
Episode 22
Inferno (4)
May 30, 1970
In a parallel England, the Doctor tries desperately to convince his captors of the immense peril they are in. But they are convinced he is a spy. And penetration zero is getting close…
Episode 23
Inferno (5)
Jun 6, 1970
The parallel Inferno has broken through the Earth's crust, unleashing terrible seismic forces and dooming the planet. The Doctor hopes to return and save his world. But the bestial primords are closing in...
Episode 24
Inferno (6)
Jun 13, 1970
The Doctor is trapped in a parallel world that is going up in flames. Can he escape in time to save Earth in his own universe?
Episode 25
Inferno (7)
Jun 20, 1970
The Doctor has escaped the catastrophic destruction of a parallel world. But can he stop Stahlman before he destroys this one?