The Surface of Thoros Beta

In the courtroom, aboard the Time Lord’s space station, The Doctor’s trial continues. The Valeyard’s next evidence, again presented via a monitor screen linked to The Matrix, is an account of The Doctor’s recent involvement on the planet Thoros-Beta in the 24th century, last quarter, fourth year, seventh month, third day.

The Doctor and Peri, his travelling companion, arrive on a coastal beach on Thoros-Beta, The Doctor having decided to investigate after learning from the dying words of a Warlord of Thordon that technologically advanced and highly dangerous weapons are being supplied from this planet. Exploring a tidal cave, the travellers are attacked by a squid-like creature, the Raak, which has apparently been stationed there to operate machinery extracting energy from the sea water. The Doctor kills the Raak with a phaser which he had acquired from the dying Warlord.

The video footage suddenly stops and The Valeyard claims that this act is proof of The Doctor's inherently violent nature. The Doctor though protests that the death of the Raak was an accident. The Valeyard’s evidence then continues showing The Doctor and Peri being captured by humanoid guards and taken to the laboratory of a scientist named Crozier, whom the guard leader had assumed they were here to see. The Doctor and Peri though manage to escape before the mistake is discovered and, in some nearby tunnels, find a wolf-creature, the Lukoser, chained to a wall. A procession of Mentors, natives of Thoros-Beta, then passes by, and amongst their number is Sil (from Thoros-Beta) - who The Doctor and Peri last met on Varos (see "Vengeance on Varos").

Peri Meets King Yrcanos

Crozier has been conducting experiments in brain transference, his ultimate aim being to transfer the brain of the Mentor leader, Kiv, into a new body, it having outgrown its own. He has also been using a cell discriminator device to pacify the belligerent King Yrcanos, a Krontep warrior, who is currently lying on a bed in the laboratory.

The Doctor and Peri make their way back to the laboratory. The Doctor starts to disconnect the circuitry but is discovered by Sil, who decides to use the cell discriminator on him. The process though has already been started when Yrcanos suddenly revives and starts smashing up the laboratory before escaping into the tunnels. Yrcanos’ actions however, did not prevent The Doctor’s mind from being affected by the process he has undergone, which has made him become callous and self-interested. He offers to help Crozier repair the lab and assists Sil with some interplanetary currency speculation. Then, totally out of character, he betrays Peri to the Mentors. His bewildered companion is chained to the Rock of Sorrows on the jagged coastline outside the city and The Doctor starts to interrogate her in an attempt to get her to confess to being a spy from Thoros-Alpha.

King Yrcanos

Back in the courtroom The Doctor objects. He claims that he cannot clearly remember these events and so is sure that the evidence being presented has been falsified. The Valeyard states that it is impossible to tamper with the Matrix and so the video footage continues with Peri being escorted back to the base for further questioning. But on their way they are ambushed by Yrcanos and so The Doctor flees. Peri then accompanies Yrcanos who reveals that he is trying to locate an Alphan resistance movement, which he assumes is present on the planet, and that the Lukoser is actually Yrcanos’s loyal equerry, Dorf, who has fallen victim to Crozier's experiments. He also makes a shock announcement to Peri that he wants her to become his bride.

When Yrcanos finds the Alphan resistance group, Peri manages to win over their leader, Tuza. They all then head for Alphans’ weapons dump but are ambushed, and taken prisoner, by the Mentors’ guards. Crozier meanwhile has found a temporary body in which to house Kiv's brain. It is that of a Mentor fisherman found floating dead in the sea. The transfer is achieved successfully after several nerve-wracking false alarms - Kiv having ordered that both Crozier and Sil be killed if the operation failed.

As neither The Doctor nor the Alphans are suitable candidates for the permanent transference of Kiv’s brain, Crozier must find another host. He therefore wonders if Peri would be suitable. The Doctor, now acting more like his true self, goes to the Induction centre - the area where new Thoros-Alphan prisoners are taken for conditioning with brain implants. There he frees Tuza, rescues Yrcanos and Dorf from a cell, before heading off to save Peri, who is being prepared to become the ultimate recipient of Lord Kiv’s intelligence. Dorf is killed by guards and, in a rage, Yrcanos destroys the control centre. This causes the Alphan slaves to start milling about in confusion as their brain implants are longer operative.

Sil

As The Doctor approaches the laboratory, to rescue Peri, he is taken out of time by the Time Lords and transported to their space station to begin his trial. The video footage continues showing the transference operation being completed successfully by Crozier, and Kiv awakening in the body of Peri, whose own mind now ceases to exist.

Yrcanos and Tuza, who had been temporarily frozen in time by the Time Lords, are released at this point and they force their way into the laboratory. Unable to stand the sight of his intended bride possessed by Kiv’s consciousness, Yrcanos fires a phaser indiscriminately about the room, destroying everything within - the result which the Time Lords had intended to achieve, to eliminate the threat which they considered the transference equipment to pose to the natural course of evolution.

Back in the courtroom The Doctor is distraught at what he has seen and angrily disputes The Inquisitor’s claim that the High Council had no choice but to intervene. The Valeyard though insists that the interference of the Time Lords was to prevent a greater disaster befalling the universe due to the actions carried out by The Doctor.

The Doctor though is not convinced and he alleges that the Time Lords had an ulterior motive for taking him out of time and thus preventing him from saving Peri. He also asserts that there is more to this trial than has so far been revealed, and that he has every intention of finding out what it is as the trial continues.