Well Queen Katryca and her tribesmen arrive at the underground bunker and decide to confront the robot Drathro, the Immortal one. Obviously Drathro was not a fan of Joan Sim's acting. I blame the lines she was given, sorry Robert Holmes.
The Doctor tries to get Drathro to spare the humans and also he tells the robot that he will repair the black light converter. The Doctor fears that if it explodes it will have disastrous consequences. Glitz and Dibber helped out in dealing with the Immortal One.
Of course by the end, The Doctor has a smug satisfied look. He has freed the humans from Drathro and prevented the black light converter from exploding.
It all makes the Valeyard's case look weak. That is the problem with the trial concept. The Valeyard accuses him of interference and causing violence and mayhem wherever he goes.
As Doctor Who fans will know. The second Doctor was charged with all this back in The War Games. The third Doctor was forgiven by the High Council of the Time Lords. Here the Doctor has ultimately helped the situation and there is still the mystery of how Earth ended up in the wrong place.
The Valeyard argues there is more evidence to present which leads to the next adventure.
Overall the story is better than I remembered from its broadcast back in 1986. That is not saying much, I just remembered the whole thing being dreadful. Now it is just less dreadful. The trial scenes just look so badly directed, almost inert and stagy.