Adric’s death has clearly shaken the TARDIS crew, but the Doctor thinks he can cheer his remaining companions by taking them to a ball. However, the TARDIS instead arrives of Heathrow airport-where Tegan was supposed to start work as a stewardess way back in Logopolis.
The Doctor and co. then try to help track down a missing Concorde, which takes them back to prehistoric times (but before Adric’s collision), where a mysterious alien named Kalid is trying to summon the aliens known as the Xeraphin.
Who turns out to be the Master in disguise:
The Master eventually gets defeated, and sent to the home planet of the aliens whose power he was trying to harness. Tegan, however, is left behind when the TARDIS returns to Heathrow.
As the Doctor and Nyssa continue on their adventures-and Tegan returns to the life of an air stewardess-intrigue is once again afoot on Gallifrey. The Time Lord founder known as Omega-who survived his encounter with the first three Doctors-has returned, and wants to return to “our” universe once again, by using the “Arc of Infinity” to bond with the Doctor and enter our universe, along with the help of a time lord traitor. However, it’s possible once Omega-composed of anti-matter-enters our ‘matter’ universe, it could destroy it. Judging the risk far too great, the Time Lords try to execute the Doctor.
Meanwhile, Tegan is in Amsterdam trying to find her missing cousin, who has vanished while in a Crypt. Turns out the Crypt is actually part of the Arc, and Omega is using it to cross over. The Doctor is not executed, but stuck in the Time Lord matrix again. Eventually, he escapes and returns to Earth to rescue Tegan and her cousin, who are captured by Omega. Omega also completes his crossover, becoming a bodily clone of the Fifth Doctor.
However, the body is unstable and decaying, and once again the Doctor is forced to kill Omega to save the universe from anti-matter. Tegan also rejoins Nyssa and the Doctor.
Next up the Mara returns-hiding in Tegan’s mind since the Kinda adventure-and redirects the TARDIS to Manussa, where it hopes to exact revenge on the civilization that assumed they had destroyed the psychic snake monster.
The Doctor eventually defeats the Mara once again, by not looking at the beast and practicing a form of meditation which weakens the creature. Tegan is at least, free of the possession of the monster.
After those kind of trippy adventures, the Doctor finds himself in a more traditional, if time-twisted one featuring the return of an old friend. After a car accident, a schoolboy-Turlough-is confronted by the Black Guardian, who wants revenge against the Doctor for the Key To Time defeat. He wants to use Turlough to kill the Doctor, and as part of the bargain, he’ll send Turlough back home (Turlough as we later find out is an exiled alien prince).It also turns out that Turlough is a student at a school where Brigadier Lethbridge-Stuart is now a teacher-and it’s his car Turlough crashed.
Meanwhile, the Doctor and co. discover a strange ship in Earth orbit. However, due to some strange time and transport shenanigans, the Doctor ends up in 1983 alone and without a TARDIS, while Nyssa and Tegan end up six years in the past.
Arriving at the school, the Doctor soon recognizes his old friend. However, the Brig doesn’t exactly remember the Doctor-and it’s not because of the regeneration. He seems to have largely forgotten about all their adventures as well (Although he still remembers UNIT).
“What would you say if I told you I was looking for my TARDIS?” “Very little”.
Fortunately, the Doctor is able to eventually revive the Brigadiar’s memory, which was suppressed due to a traumatic event in the past. The Doctor mentions that he’s stuck without his TARDIS and companions…however mentioning Tegan causes the Brig to recall that he’s met the girl before, in 1977, much to the Doctor’s surprise.
In 1977, Tegan also meets the Brig in his younger incarnation. Turns out the time divergence is the result of the machinations of an alien called Mawdryn, part of a group of aliens who stole time lord regeneration technology so they could be immortal, but unfortunately their regenerations have gone wrong making them deformed mutants living in eternal agony. Manipulating the Doctor, they want him to selflessly give up his remaining regenerations so that it will help them die. Turlough, in the meantime, begins to doubt the Black Guardian’s intentions as he sees more of the moral character of the Doctor as he accompanies the Doctor and Brig.
Eventually, the Doctor agrees to transfer his regeneration energy to Mawdryn’s crew, but something unexpected occurs. The 1977 Brigadier-traveling with Tegan and Nyssa to the spaceship-meets the 1983 Brigadier, causing the machine to short circuit, killing the mutants. The same incident also messes up 1977 Brigadier, causing him to lose his memory of the Doctor in the first place. The Doctor returns his old friend home, and Turlough joins the TARDIS crew.
Their next adventure-due to Turlough’s sabotage under orders from the Black Guardian- takes them to the outer space “leper colony” Terminus, which is actually in the center of the universe, and one of it’s engines sort of created the big bang, and could cause a second big bang if not repaired. Nyssa also begins to suffer from the colony’s disease, however she is eventually cured, and stays behind to help develop a cure, while the Doctor is able to stop the second engine igniting.
The next adventure finds the Doctor in a boat race-in space, with immortal creatures called “Eternals” in a competition. The Black Guardian tries to use Turlough once again to kill the Doctor, but Turlough instead refuses and betrays the Guardian, becoming a full, more trusted companion of the Doctor’s crew.
After a somewhat goofy adventure where the Doctor battles the Master in medieval times, and gains a new robot companion Kamelion (Who doesn’t do much), the anniversary special begins. The Five Doctors.
Somebody is kidnapping the various Doctors, their enemies, and their companions from various points in time and space, and depositing them in the “Death Zone”, an ancient wasteland on Gallifrey, which also holds the tomb of Gallifreyan founder Rassilon. The First Doctor is sent with his granddaughter, Susan; the Second with the (1983) Brigadiar, The third teams up with the older Sarah Jane Smith. The Fourth Doctor, K-9 and Romana unfortunately, get stuck in a ‘time eddy’ similar to where the First Doctor would up in the last Doctor team up.
The Fifth Doctor feels the after-effects of all this, and in a weakened state also sets the TARDIS for Gallifrey. Meanwhile, the Master is summoned by the high council, and told to help the Doctor.
The various Doctors reason that their solution is to go to the tower and try to figure out what’s going on, and are confronted by various Daleks, Cybermen, and Yeti on their way. The Fifth Doctor, not trusting the Master, manages to transport himself to the high council, where he discovers that it’s likely a time lord traitor is responsible for this whole mess.
The Five Doctors, sort of. Richard Hurdnall replaced the deceased William Hartnell, Tom Baker didn’t want to appear hence he was largely written out, and this is a wax dummy. Pictured are Hurdnall, Patrick Troughton, Jon Pertwee, the dummy, and Peter Davison along with K-9 Mark III, Elisabeth Sladen, Carole Ann Ford (Susan) and Nicholas Courtney.
He eventually discovers it’s Borusa, time lord president and one of the Doctor’s mentors. Borusa has basically tried to use the combined Doctors to help get him into the tower, disable it’s force fields which prevent him from teleporting there. His reason is that Rassilon’s corpse is in possession of a ring that would give Borusa immortality (Although Time Lords regenerate and as a result live very long lives, they are not immortal). Borusa almost succeeds, as Rassilon’s spirit appears and lets Borusa take the ring. However, due to a gambit by the first Doctor, the ring gives Borusa a cursed form of immortality, turning him into a stone relief on Rassilon’s tomb.
The various Doctors bid their farewells and return to their respective times. The Fifth Doctor briefly stays behind, and learns that the High Council wants to make him Time Lord president due to Borusa vanishing and his help in stopping him. However, the Doctor and co quickly leave in the TARDIS, the Doctor deciding to once again resume his adventures.
“TEGAN: You mean you’re deliberately choosing to go on the run from your own people in a rackety old Tardis?
DOCTOR Why not? After all, that’s how it all started.”