Another adventure for everyone's favourite time-traveller. Answering the Brigadier's space/time telegraph, the Doctor (Tom Baker), Sarah (Elisabeth Sladen) and Harry (Ian Marter) arrive in the village of Tulloch, near Loch Ness. A series of attacks have taken place on local oil rigs, and many are blaming the legendary monster. The Doctor discovers the creature to be the Skarasen - cyborg pet of invading aliens the Zygons. Their own planet having been destroyed and their spaceship crippled, these deadly shape-shifters are now intent upon taking control of the planet Earth.

Another adventure for everyone's favourite Time Lord. The Doctor (Jon Pertwee) and Jo (Katy Manning) travel to Stangmoor prison to investigate a machine which can remove evil from the minds of criminals. However, the man behind the scheme - Professor Kellerman - is in fact the Doctor's arch-nemesis, the Master (Roger Delgado), and is planning to disrupt a United Nations peace conference. Inside the Master's machine is an alien parasite which can make people see their greatest fears, and is growing stronger all the time. Can the Doctor stop both the Master and the unearthly parasite?

The last adventure to star Jon Pertwee. To save the Universe, the Doctor must travel to the planet Metebelis Three, where he discovers an invasion plan of Earth by the Metebelis Spiders, under the leadership of the Great One. To save the planet the Doctor must absorb a lethal dose of radiation, triggering his third regeneration...

The newly regenerated Doctor (Tom Baker), assisted by Sarah, Harry and the Brigadier, has to track down the theft of the components for a powerful new laser gun, and the death of a prominent politician. Sarah investigates the mysterious Think Tank, where it becomes clear that robot K-1 is being misused by its political extremist masters and the Doctor has to prevent the robot from being used to start an atomic war. Tom Baker's first story as the Doctor.

Another adventure for everyone's favourite Time Lord. UNIT is called to a sleepy mining town in South Wales to investigate the mysterious death of a miner in an inactive pit. The Wholeweal environmental community believe that a local chemical company has something to do with the death, and when the Doctor heads a mission down the mines he discovers thousands of maggots surrounded by poisonous slime. Further investigation at the chemical works reveals the owner to be under the malign influence of a sentient computer, BOSS.

Another adventure for everyone's favourite Time Lord. The arrival on Earth of a UFO brings with it the Axons - golden-skinned aliens who offer the gift of Axonite to mankind. The Doctor (Jon Pertwee) is suspicious, especially when he discovers that his old enemy the Master (Roger Delgado) is on board the Axon craft.

Jon Pertwee stars as the time travelling Doctor, who once more finds the planet under threat. Trying to avert a war which will bring Earth under the domination of the Daleks and their ferocious slaves (the Ogrons), the Doctor fights one of the biggest challenges he has faced so far.

Another adventure for everyone's favourite Time Lord. Still chafing at his exile to the planet Earth, the Doctor (Jon Pertwee) is called in to observe the Inferno drilling experiment of Professor Stahlman (Olaf Pooley). Stahlman's search for a new form of energy goes horribly wrong when a green slime emitted from the drill site transforms any who come into contact with it into primeval monsters. Meanwhile, after experimenting with the TARDIS console, the Doctor finds himself transported sideways in time to a parallel version of the Earth, where the Brigadier (Nicholas Courtney) is an eyepatch-wearing fascist and Stahlman's experiments threaten to destroy the world.