The stories in the sixteenth season of Doctor Who were all part of an overarching storyline in which the Doctor and his new assistant Romana searched throughout time and space for segments of a powerful artifact called the Key to Time. The story added to the cosmology of the series by introducing the Guardians, quasi-mystical beings whose power is superior to the Time Lords. Also, the presence of Romana, a “Time Lady” from the Doctor’s home planet, allowed some interesting details of the Doctor’s biography to be revealed.
From “The Ribos Operation”
The Doctor has just decided to take a long holiday when the TARDIS is seized by the White Guardian, who tells the Doctor he requires his assistance in tracking down the six segments of the legendary Key to Time so that they can be reassembled in order to use its power to restore the balance of the forces of the universe. The White Guardian warns the Doctor of the threat posed by the Black Guardian, who wants the Key to Time for his own evil purposes. The White Guardian also provides the Doctor with an assistant, a young Gallifreyan woman whom the Doctor nicknames Romana.
Romana: My name is Romanadvoratrelundar.
The Doctor: I’m so sorry about that. Is there anything we can do?
Romana: The President of the Supreme Council sent me. I was told to give you this.
The Doctor: What’s this?
Romana: According to my instructions, it’s the core to the Key to Time. Very exciting, isn’t it?
The Doctor: Yes, I suppose it must be, for someone as young and inexperienced as you are.
Romana: I may be inexperienced, but I did graduate from the Academy with a triple-first.
The Doctor: I suppose you think we should be impressed by that, too?
Romana: Well, it’s better than scraping through with 51% at the second attempt.
The Doctor: That information is confidential! That president-- I should have thrown him to the Sontarans when I had the chance!
When the core is linked to the main console, the TARDIS materializes on the planet Ribos, where they find the first segment disguised among the local crown jewels. Romana mentions that she is nearly 140 years old. She says the Doctor is 759, but he admits to only 756.
Lady Romanadvoratrelundar was apparently unaware of the involvement of the Guardians when seemingly chosen by the Lord President of the High Council of the Time Lords to assist the Doctor in reassembling the Key to Time. While possessing a great deal of book-learning, she is woefully inexperienced to the ways of the world. She tells the Doctor she was “willing to be impressed” until meeting him, implying the Doctor has something of a reputation among his people. She seems eager to prove herself, probably feeling greatly honored to leave Gallifrey for such an important mission, mentioning she might write her thesis on the Doctor’s psychological maladjustments. Her attitude changes as she experiences life outside the shelter of Time Lord society, though, and after going through her first regeneration, she loses interest in returning to Gallifrey at all, choosing instead to live in E-Space and follow the Doctor’s example of getting involved, using information stored in K-9’s memory banks to build a TARDIS of her very own.
From “The Pirate Planet”
Romana is reading the flight manual as the Doctor prepares to take them to the second segment of the Key to Time. She mentions that vintage vessels like the Type 40 were an optional course at the Academy that she didn’t bother with.
Romana: Doctor, what about the synchronic feedback checking circuit?
The Doctor: What about it?
Romana: Aren’t you going to set it?
The Doctor: No, no, no, I never bother about that. Complete waste of time.
Romana: According to the manual, it’s essential.
The Doctor: Listen, have you any idea how long I’ve been operating this TARDIS?
Romana: Five hundred and twenty-three years.
The Doctor: Right -- ! Is it really that long? My, how time flies.
Romana: Hasn’t it. And the multi-loop stabiliser?
The Doctor: What?
Romana: The multi-loop stabiliser. It says here, “On any capsule, it will be impossible to effect a smooth materialisation without first activating the multi-loop stabiliser.”
The Doctor: Absolute rubbish!
The TARDIS tries to materialize on the barren planet Calufrax, but instead lands on Zanak, which has itself materialized around Calufrax in order to plunder its mineralogical resources. The Doctor, Romana, and K-9 defeat the pirates only to learn that the entire planet of Calufrax is the second segment of the Key to Time.
If the Doctor is, in fact, 759 years old and has been operating the TARDIS for 523 years, then he must have been 236 years old when he and Susan first left Gallifrey. The two of them apparently led a fugitive life for an undetermined amount of time until the Doctor was able to hide the Hand of Omega on Earth. The Time Lords seemed to lose interest in him for a while after that.
From “The Stones of Blood”
The Doctor decides to tell Romana the whole story behind their mission after the White Guardian warns them again to beware of the Black Guardian. The Doctor believes the White Guardian assumed the form of the Lord President in order to contact Romana, so the Time Lords may not even know about their mission. The locator directs the TARDIS to Earth, where they find an ancient stone circle and get mixed up with druidic cultists and the alien fugitive from justice whom they worship. This alien had stolen a powerful object from her home planet and used it to set herself up as a goddess on ancient Earth, an object which proves to be the third segment of the Key to Time.
From “The Androids of Tara”
When the TARDIS materializes on the planet Tara, the Doctor decides he’s going to take a day off while Romana finds the fourth segment of the Key to Time. Romana says she has checked their records and found a suitable Taran outfit in the wardrobe room, which she seems to have organized. She soon finds the fourth segment, only to get mixed up in the political machinations of a local nobleman who wishes to use Romana’s remarkable resemblance to Princess Strella in his bid to seize the throne. The Doctor falls in with the rightful heir, who plans to use an android double to outwit his enemies.
From “The Power of Kroll”
The TARDIS materializes on the third moon of Delta Magna, a swampy world where tensions run high between the native population and a chemical refinery run by Earth colonists. The natives worship a giant squid called Kroll, which was a normal squid until swallowing the fifth segment of the Key to Time. While being stretched to death on a primitive rack, the Doctor vocalizes a high-pitched tone that shatters a window, allowing rain to fall on his bonds, rendering them elastic.
From “The Armageddon Factor”
As the TARDIS materializes on the planet Atrios, the Doctor, Romana, and K-9 worry that the Black Guardian may finally show his hand. The planet is engaged in nuclear war with the neighboring planet Zeos. The Doctor is taken prisoner by a mysterious figure calling himself the Shadow, who demands the Doctor surrender the five segments of the Key to Time locked inside the TARDIS.
The Shadow: I have waited so long, even another thousand years would be nothing for me. But you -- I have watched you in your jackdaw meanderings. I know you, and I know there is a want of patience in your nature.
The Shadow has created an automated war computer on Zeos to make sure the war continues. In order to stop the computer from blowing up both planets in a final gambit, the Doctor manufactures a temporary sixth segment and uses the Key to Time to create a three-second time loop. However, as the artificial segment degrades, the time loop stretches. The Doctor tracks down the Shadow, who reveals that he serves the Black Guardian. The Shadow imprisons the Doctor, where he meets a fellow prisoner, Drax, who is himself a “fallen” Time Lord and an old school chum of the Doctor’s, who’s been living as a sort of intergalactic handyman. Drax at first calls the Doctor by his academy nickname of “Theta Sigma.” Five years previously, Drax unwittingly helped the Shadow build the Zeon war computer before being taken prisoner.
The Doctor: Drax, I don’t want to pry, but where did you acquire this peculiar vocabulary?
Drax: Brixton, wudn’t it?
The Doctor: Brixton?
Drax: Brixton. London. Earth.
The Doctor: I’ve been to Earth.
Drax: Well, me transport broke down -- hyperbolics, as usual -- and I was investigatin’ certain possibilities with regard to replacements… I got done, didn’t I? Ten years I got. Well, I had to learn the lingo, didn’t I, to survive. Why, is there something funny about the way I talk?
The Doctor: No, no, it’s very colourful. Very demotic.
Drax: Well, thanks, Theet.
The Doctor: Doctor.
The Doctor, Romana, K-9, and Drax escape from the Shadow with all six segments, the sixth of which was Princess Astra of Atrios herself. A missile attack destroys the Shadow and his spaceship, his punishment for failing the Black Guardian being death. Drax sees opportunity rebuilding war damage on both planets and departs, leaving the Doctor and Romana to deal with the completed Key to Time. Disguised as the White Guardian, the Black Guardian tries to convince the Doctor to surrender the Key to Time, but the Doctor sees through the deception when the Guardian shows little concern for the fate of Princess Astra. The Doctor breaks the core rod and the six segments once again scatter throughout space and time. The Black Guardian vows to destroy the Doctor, necessitating that the TARDIS guidance system be fitted with a randomizer, which prevents even the Doctor from knowing where they’re headed next.