The Sixth Doctor (Colin Baker) is being put on trial by the Time-Lords of Gallifrey at one of their space stations. The prosecutor, called the Valeyard (Michael Jayston) shows video from the Matrix concerning the Doctor on the planet Thoros Beta.
The Doctor and Peri arrive on Thoros Beta, as the Doctor wants to see the advanced weaponry possessed by the Warlords of Thorodon. In the caves, the Doctor discovers Sil (Nabil Shaban) a diminutive aquatic creature who is supplying the weapons from the Mentors. A scientist named Crozier (Patrick Ryecart) is working for Sil to transplant the mind of Kiv (Christopher Ryan), Sil’s superior, into a younger, healthier body. Discovered, the time-travellers escape with the Warlord King Yrcanos (Brian Blessed).
The Doctor, Peri, Yrcanos and his men plan to attack Sil, but the Doctor betrays them by warning the Mentors, causing Peri and Yrcanos to flee in different directions. With the help of one of the Mentors’ servant women, Peri disguises herself to get close to the Doctor. The Doctor reveals Peri to the Mentors and asks to interrogate her alone. Secretly, he tells her his betrayal was a ploy to uncover Sil’s plan; they will transplant Kiv’s mind into his body if he does not cooperate.
Crozier interrupts the interrogation to get a crack at Peri himself. But Yrcanos arrives to kill the Doctor. Peri stops Yrcanos and they escape, meeting up with Yrcanos’ men. As Kiv lies dying, Crozier is forced to transplant his brain, with the Doctor’s help, into the body of a servant. Yrcanos, Peri, and his men attack a weapons stash, but are captured. Sil and Crozier decide to transplant the brain into Peri’s body, despite the Doctor’s objections. As the operation is being prepared, the Doctor sneaks away and frees Yrcanos to try to save Peri.
Peri is strapped down and gagged, and Crozier gives the order to shave her head. The Doctor attempts to save her, but at that moment is drawn away to the TARDIS. He is taken to the trial at that point. The Doctor accuses the Time-Lords of putting Peri’s life in danger, but the Valeyard says the Doctor should not have been involved in the first place. On Thoros Beta, Yrcanos is placed in a time-bubble by the Time-Lords and Kiv’s mind is placed in Peri’s body. When Yrcanos is freed, he is distraught and fires his gun wildly, killing Peri. The Valeyard says the Time-Lords’ interference was to prevent a greater disaster befalling the universe because of the Doctor—namely, this business of preventing death by the transference of minds. I’m not sure the Time-Lords are on the high road here. The Doctor vows to find out the truth.
Deep Roy, another small actor who had played Mr. Sin in the Talons of Weng-Chiang, appears as a Posticarian delegate. Yrcanos is King of the Krontep, Lord of the Vingten, and Conqueror of the Tonkomp Empire. Brian Blessed pretty much steals the show. He turned down a major film for it, modeling his performance on his role of Prince Vultan in Flash Gordon, which, like this one, was written for him. John Rhys-Davies, Derek Jacobi, and David Warner had also been considered. His helmet was obviously inspired by the Samurai. He thought the production an unhappy one because of the threatened demise of the series. Phil Collins was considered for Crozier. Trevor Laird, who played the guard Captain Flax, would later have a continuing role as Martha Jones’ father in the David Tennant years. Sil first appeared in Vengeance on Varos; at the time, we thought it was a hideously dark story. He has changed from brown to green. In Crozier’s lab is a preserved Alien Chestburster.
The music by Richard Hartely is arresting, the only score he did for Doctor Who, and it was not kept by the BBC. The special effects are rather better than usual, particularly the TARDIS landing in a striking pink ocean under a green sky. Brian Blessed—bless him—begins slightly over the top and goes up from there. He shouts and laughs and whispers and whistles and threatens good-natured mayhem upon his enemies. Sil is a gloriously and literally slimy villain, uproariously evil, and Crozier is a calm and reasonable lab coat Nazi of a mad scientist. The Doctor is bombastic and voluble as usual, either scheming or twisted—we never find out which. Peri does an unexpected acting turn when she awakes from surgery, bald-headed and cold-eyed, and speaks in the sepulchral voice of the evil Kiv.
Colin Baker himself was not clear about this flawed Doctor’s behaviour in this story; was he really that evil, or was the Gallifreyan Matrix lying? He thought it was sloppy and cobbled together. It seems like it could have been a great story if it had not been weighed down by the Trial of a Time-Lord baggage. When Adric was killed off in Earthshock, we were shocked that a companion would be killed, however nobly. In this one, Peri was bound and gagged, had her head shaved and her brain removed, and an alien sea-creature’s brain substituted, and then she was shot dead. The uncomfortable truth is that Peri is a sex-object being tortured. One could even consider this the role of female Who companions in general, considering all the kidnappings and bondage and human sacrifice, though usually disguised with movie-serial melodrama to prevent it from being taken too seriously.