Joining the Doctor and Sarah on their travels is new companion, Harry Sullivan. Harry is a medical officer working for U.N.I.T. who was called in to check on the newly regenerated Doctor.
The TARDIS takes the Doctor, Sarah, and Harry to the far future, arriving at the Ark space station, where they discover mankind in hibernation. At a different points in time, they also encounter the Cybermen and the Sontarans.






UNIT are called in when top secret plans and valuable equipment is stolen from high security establishments.
Using the deadly disintegrator weapon, the robot steals the destructor codes.
Sealed inside an underground bunker, Miss Winters issues her demands to the world's leaders.
The robot, distraught over killing its creator, takes Sarah hostage and goes on a rampage.
The survivors of mankind are in cryogenic suspension aboard the Nerva Beacon space station.
The survivors of the human race start to awaken. But Perhaps not all of them are entirely human.
Humankind faces total destruction. Can the Doctor defeat the Wirrn?
Trapped by the Wirrn, The Doctor and his friends are forced into one last terrible gamble.
Arriving on Earth, the Doctor, Harry and Sarah meet a group of stranded human colonists.
Sarah has been captured by Styre who is conducting experiments on the captured humans.
The Time Lords send the Doctor to Skaro at a point in time shortly before the creation of the Daleks.
The Doctor finds that some of Davros’s fellow Kaleds are unhappy with the development of the Daleks.
The Doctor informs the Kaled government of Davros's experiments and they move to shut down the bunker.
When the Kaled dome is destroyed by the Thals' rocket, the war appears to be over.
Davros interrogates the Doctor, forcing him to reveal the future of the Daleks.
The Kaled scientific elite move to prevent the development of the Daleks.
The Doctor, Sarah and Harry return to the Nerva Beacon space station, but at an earlier point in time.
Sarah is the latest victim of the space plague and the only way to cure her is by transmatting her to Voga.
The Doctor and two of the Nerva crew become walking bombs which the Cybermen plan to detonate.
Their plan to blow up Voga thwarted, the Cybermen intend to crash Nerva into the planet.
Fourth Doctor
Tom Baker
Sarah Jane Smith
Elisabeth Sladen
Harry Sullivan
Ian Marter
Davros
Michael Wisher
Nyder
Peter Miles
Gharman
Dennis Chinnery
Ravon
Guy Siner
Time Lord
John Franklyn-Robbins
Kaled Leader
Richard Reeves
Sevrin
Stephen Yardley
Ronson
James Garbutt
Tane
Drew Wood
Gerrill
Jeremy Chandler
Thal Soldier
Pat Gorman
Kavell
Tom Georgeson
Mogran
Ivor Roberts
Thal Politician
Michael Lynch
Thal Soldier
Hilary Minster
Thal Guard
Max Faulkner
Bettan
Harriet Philpin
Kaled Guard
Peter Mantle
Kravos
Andrew Johns
Thal Soldier
John Gleeson
Fourth Doctor
Tom Baker
Sarah Jane Smith
Elisabeth Sladen
Harry Sullivan
Ian Marter
Kellman
Jeremy Wilkin
Commander Stevenson
Ronald Leigh-Hunt
Lester
William Marlowe
Warner
Alec Wallis
Vorus
David Collings
Magrik
Michael Wisher
Cyberleader
Christopher Robbie
Tyrum
Kevin Stoney
Sheprah
Brian Grellis