Season twenty-three of Doctor Who was presented as a single serial under the title “Trial of a Time Lord,” with four interrelated yet distinct segments. A new companion was introduced in a rather convoluted manner as Peri was written out. This would prove to be the last story featuring the Time Lords. It also proved to be the final adventure for the sixth Doctor, as Colin Baker was fired before production began on the following season.
From “The Mysterious Planet”
The Doctor is forcibly brought aboard a gigantic deep space station to once again stand trial in a Time Lord court for conduct unbecoming a Time Lord and for meddling in the affairs of other cultures. The Doctor learns that since he neglected his duties as Lord President of the High Council of the Time Lords, he has been removed from office. The Valeyard, acting as prosecutor, presents what he considers a typical example of the Doctor’s meddling activity culled from the data stored in the Matrix. The Valeyard explains that the Time Lords are able to carry out detailed surveillance upon anyone within range of a TARDIS. His first example is the Doctor’s recent visit to Ravolox, during which time the Doctor claimed to be 900 years old (At one point, he also produced from his patchwork coat a bag of jelly babies.) After encountering intergalactic highwayman Sabalom Glitz, who was attempting to steal secret tapes from an abandoned Andromedan base, the Doctor realized that Ravolox was really Earth, mysteriously moved across the galaxy. However, it becomes apparent that the High Council is suppressing certain information within the presented evidence. During the course of the trial, the Doctor’s utter contempt for Time Lord society becomes evident.
The trial continues with a presentation of the Doctor’s activities immediately preceding his summons to the Time Lord court, at which time he and Peri Brown were investigating arms shipments from Thoros-Beta, homeworld of Sil, an enemy they made on Varos. The Doctor realizes during the presentation that he has lost his memory of the events being shown. When they present him teaming up with Sil and aiding his evil scheme, the Doctor suspects the evidence has been tampered with, despite the inviolate nature of the Matrix. At the conclusion of the evidence, the Doctor is shown how, after transporting him and the TARDIS away, the Time Lords apparently manipulated events so that King Yrcanos destroyed Crozier and his mind-transference experiments, killing Peri in the process.
From “Terror of the Vervoids”
The trial continues following a brief recess to allow the Doctor time to deal with Peri’s death and to search the Matrix for evidence to present in his own defense. He presents an episode from his near future, at which time he is traveling with a young woman named Mel. However, the Doctor becomes convinced during the presentation that the evidence has been tampered with to incriminate him before the court. Unfortunately, by showing himself destroying every last Vervoid, the Doctor opens himself to the charge of genocide, which the Valeyard immediately puts before the court.
From “The Ultimate Foe”
Responding to the Doctor’s charges of malfeasance, the High Court of the Time Lords brings the Keeper of the Matrix in for questioning However, the proceedings are interrupted by the arrival of both Sabalom Glitz and Mel, who, it turns out, were sent for by the Master, who has been observing the trial from within the Matrix. The Master finally shows himself to the assemblage, claiming to intervene for the sake of “justice.” Under the Doctor’s examination, Glitz reveals that the Andromedans were hacking information from the Time Lord’s Matrix from a secret base on Earth. To prevent these secrets from coming to light, the High Council ordered that the Magnetron be used to move the planet, and that it be renamed Ravolox. Learning of this, the Master had hired Glitz to recover the secrets. The Doctor is outraged:
The Doctor: In all my travelings throughout the universe, I have battled against evil, against power-mad conspirators! I should have stayed here! The oldest civilisation, decadent, degenerate, and rotten to the core! Power-mad conspirators? Daleks, Sontarans, Cybermen? They’re still in the nursery compared to us! Ten million years of absolute power, that’s what it takes to be really corrupt!
The Master then reveals that in order to stop the Doctor from uncovering more of its secrets, the High Council struck a deal with the Valeyard, who is an amalgamation of the darker sides of the Doctor’s own character from somewhere between his twelfth and final incarnations. The Master also reveals that Peri did not, in fact, die, but instead was saved by King Yrcanos and taken back to Krontep to be his queen. Once news of the scandal leaks out, the Keeper tells the Inquisitor that the High Council has been deposed and insurrection has broken out on Gallifrey. The Master’s triumph is short-lived, though, as he and Glitz become trapped within the Matrix, awaiting justice from the new Time Lord government. The charges against the Doctor are dropped, although the Valeyard makes good his escape.
Upon being released, the Doctor and Melanie Bush leave the space station in the TARDIS. However, while it is clear that Mel is well-acquainted with the Doctor, he has never actually met her before. Also, the Doctor has yet to actually encounter the Vervoids aboard the Hyperion III, although Mel remembers that adventure well. Presumably, to untangle this mess, the Doctor had to leave Mel somewhere and go off on his own to their actual first meeting and their encounter with the Vervoids, during which time he perhaps endured a self-imposed amnesia. They would then continue on until whatever point in time Mel was summoned by the Master. The Doctor would have to leave her again shortly before this and then pick her up shortly after his past self dropped her off. Mel would perhaps not even be aware of the Doctor’s measures, thinking the trial merely occurred at that point in a simple linear fashion. They would then continue on together to Lakertya and the Doctor’s regeneration before finally parting company on Iceworld, where Mel partnered up with Sabalom Glitz aboard the Nosferatu II.