The Doctor has just learned that Peri died in the previous episode, but the show must go on. Or in the Doctor's case, his trial must go on. Given the same opportunity as the Valeyard, the Doctor draws upon the Matrix as his evidence. His defence (at least to the Valeyard) is he improves in the future. To illustrate this, he highlights an adventure that take place in the future, with a future companion; Melanie.
The adventure begins when the Tardis suddenly receives a distress call. Quickly the Doctor answers it and the Tardis materializes inside the Hyperion III. Initially, Rudge, the security chief apprehends the Doctor and Mel - not knowing how they got inside the ship. The Doctor is taken to Commodore Travers, who already knows the Doctor from a previous unseen adventure. Knowing the Doctors reputation for running into trouble, Travers is none to pleased to meet him.
The Doctor is set to work immediately as one death has already taken place. Mel decides she wants to investigate the hydroponics bay, but the Doctor dismisses her and the lead she's following up on. Immediately, the Doctor (back in the court-room) halts the matrix. He claims the Matrix has been tampered with as he wouldn't have dismissed Mel and her evidence. Again, the Valeyard claims the Matrix cannot be altered. Reluctantly, the Doctor decides to continue airing the episode. He hopes it'll give him a clue to who's trying to frame him and how.
It isn't long before the episode is once again interrupted when the Valeyard questions the Doctor on seeming to have additional information than what the court room has. He accuses the Doctor of omitting evidence. The Doctor, however, is able to support his evidence by reshowing a crucial part with the Mogarians and the Commodore. Two of the Mogarians turn on their translators before talking, but one does not. However, the Mogarians are peace loving people so it's unlikely they are the culprits behind the now several murders.
Despite being peace loving, the Mogarians voice their views of the humans who they think are taking advantage of some mining rights. As their innocence seems unsteady, another group appear with some shady motives. Lasky and her associates have a cabin which remains locked at all times with a guard standing duty. Horrible moans and crashing can be heard within at times. In the fitness centre, one of the group talks about the disturbing aspect of their research and has his doubts about their research.
Inclined to investigate this tight lipped group, Mel convinces the Doctor of the urgency. After breaking into the isolation room, the Doctor and Mel are shocked to find a human/plant hybrid. This is the questionable research the group have been working on. Currently they are en route to Earth where professor Lasky hopes to cure the woman. The Doctor and Mel are ushered out of the isolation room so the hybrid can be sedated. But there is still the problem of the mysterious deaths.
As if problems aren't bad enough, it's soon revealed that Security Chief Rudge is hijacking the freighter along with the Mogarians. The Mogarians wish to 'liberate' the minerals mined from their planet and are paying Rudge for his help. As he's reaching retirement, he's hoping for a more secure future. But Mel is able to sneak away and warn the others. The hijacking is thwarted.
Despite all the motives floating around, the real culprits behind all the murders are the Vervoids. A species created by Professor Lasky and her companions. Mel is shocked when she discovers their human compost heap, but the Doctor reminds her it's all relative. It's no more unusual for the plant-like Vervoids to compost humans as it would be for humans to do so with discarded plants. Essentially, the Vervoids are acting completely out of instinct in order to preserve their race.
Realizing how dangerous the Vervoids can be, The Doctor orchestrates their demise by using a rare metal that accelerates their growth. The Vervoids wither and die in seconds, not so much as a leaf survives. The Doctor concludes his testimony, satisfied with the results. But the Valeyard gleefully acknowledges the original charge the Doctor is facing is moot. He now faces a much greater charge, GENOCIDE!
WHO: Melanie Bush
PLANET OF ORIGIN: Earth, circa 1986
REASON FOR JOINING: There is no televised encounter of Mel and the Doctor's first meeting.