The Doctor (Colin Baker) is forced to land the TARDIS on a Gallifreyan space station and is taken into a courtroom. The Inquisitor (Lynda Bellingham) declares the Doctor on trial for conduct unbecoming a Time-Lord, evidence to be presented by the Valeyard (Michael Jayston). Video footage from the Matrix shows the Doctor willingly involved with the planet Ravolox, which the Doctor denies.
The Doctor and Peri (Nicola Bryant) are shown landing on the planet and speak of how similar it is to Earth. The Doctor knows that the planet ended in a fireball, but the abundance of plant-life makes him suspicious. They encounter Sabalom Glitz (Tony Selby) and Dibber (Glen Murphy), mercenaries trying to destroy the black light generator of the L3 Robot deep underground. The Doctor and Peri find a tunnel leading to what appears to be the ruins of the Marble Arch Tube Station of the London Underground Central Line. The Doctor presses on, but Peri is frightened and remains behind.
Peri is captured by a surface tribe led by Queen Katryca (Joan Sims), who informs Peri she will have to take many husbands for the tribe. She is locked up with Glitz and Dibber, who were seized because the generator they wish to destroy is a totem for the tribe. The three overpower the guards and escape, after planting a bomb on the Black Light Generator. Black Light, incidentally, is energy from Quantum Meta-fluctuates in the Space-Time Continuum, not something to make your posters look cool.
Underground, the Doctor is captured by humans guarded by the Immortal and brought before the very L3 Robot that Glitz and Dibber are looking for. Its name is Drathro (voice of Roger Brierley) and it maintains the habitat in the underground system. Drathro orders the Doctor to make repairs to various systems, but the Doctor electrifies the robot and escapes, pursued by another robot sent by Drathro.
Peri, Glitz, and Dibber encounter the Doctor in the ruins of Marble Arch, the tribe on one side and the robot on the other. The tribesmen disable the robot and recapture the fugitives. The Doctor tries to explain that Ravolox is Earth. Drathro reactivates the service robot and sends it to the village after the Doctor, but it is disabled once again. Queen Katryca, played with warrior-queen histrionics by Joan Sims from the Carry On movies, decides to attack Drathro’s castle to steal its technology. The Doctor and Peri escape, but the Black Light Generator is now seriously damaged and if it self-destructs and starts a chain-reaction, it could take the universe with it.
Drathro defeats the Queen and the tribe. The Doctor arrives and pleads to Drathro to shut himself down, but the robot refuses. Glitz, Dibber, and Peri are brought in and Glitz offers to take the robot aboard his ship, which has a working Black Light system, to which Drathro agrees, but he is destroyed. The Doctor reconfigures the system so its self-destruction will only take the underground system with it. Everyone escapes in time. Those living underground come up to the renewed surface, and the time-travellers leave. At the trial, the Doctor declares that he saved the universe many times, but there is more prosecution to come.
This is the first part of a four-part serial called the Trial of a Time-Lord—four stories in fourteen episodes, taking up the entire 23rd Doctor Who season of 1986. In each, the Doctor is on trial by the Time-Lords for various crimes, mainly being a do-gooder who violates the Gallifreyan version of the Prime Directive. Later, they add genocide, and probably illegal TARDIS parking. The series had already been cancelled, but public pressure forced the BBC to come up with this rather uninspired compromise for another season. Not only the Doctor, but Doctor Who itself was on trial.
The opening shot of the Time-Lord space station and the TARDIS being pulled in was the most expensive model shot in the classic series. It pretty much used up the entire special-effects budget and later episodes had to fall back on the old crappy laser-beams. This serial was written by Robert Holmes, a Who stalwart of long standing. Roger Brierley (voice of Drathro) was supposed to play the robot as well, but his six-foot-four frame would not fit in the costume, so a special-effects assistant, Paul McGuiness, who had helped design the costume, wore it on camera. Ravolox is the planet Earth two million years from now and moved a couple of light years to the Stellan Galaxy. The tribe has three sacred books: Moby Dick, The Water Babies, and U.K. Habitats of the Canada Goose.
Dominic Glynn scored the incidental music, and John Nathan-Turner let him rewrite the opening theme music for the whole short season, which is haunting and one of my favourite Doctor Who themes. Sabalom Glitz is from Salastopus in the constellation Andromeda, a polygamous society. He has been to prison often, seen many psychiatrists, and is wanted in six galaxies. He reappears later in the series and figures in the trial shenanigans. The story was widely panned, but the relationship between the Doctor and Peri is sweet and charming, for a change. Script-writer Eric Saward quit a few months later. Peri was now dressed more demurely, because of complaints about her often prominently displayed charms. I can’t help but think this move did not help attract more viewers.