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...

Two classic Doctor Who adventures set on the planet of Peladon, starring Jon Pertwee as the Third Doctor, with Katy Manning as his companion in the first story and Elisabeth Sladen in the second. In the four-parter 'The Curse of Peladon' (1972), the Doctor (Pertwee) finally seems to have escaped his exile to Earth when he manages to transport Jo (Manning) in the Tardis to the planet Peladon. The pair are mistaken for Earth delegates at a conference to decide whether Peladon should join the Galactic Federation, and discover that someone is attempting to use the legendary royal beast of Aggador to trigger off a war. In the six-parter 'The Monster of Peladon' (1974), the Tardis arrives on the Planet of Peladon half a century after the Doctor's first visit. The planet has now become of great tactical importance because of its focal position between warring factions. The Doctor and Sarah (Elisabeth Sladen) have to act as peacekeepers between rival ambassadors and they must also find the truth behind 'the spirit'.

Another adventure for the intrepid space/time traveller. The Doctor (Tom Baker) has returned the TARDIS to his home planet of Gallifrey, but why has he forbidden Leela (Louise Jameson) to accompany him? Why, upon claiming the Presidency, does he expel every senior Time Lord to the outer wastes? And what plan is he hatching with the hostile Vardans? The only people he seems to have taken into his confidence are K9 and Chancellor Borusa, but whatever game the Doctor is playing, he has reckoned without the return of an old foe... This story marks the departure from the series of Leela and K9 Mark 1.