The Doctor and Mel are taking a rest aboard the Hyperion III when a series of murders lead them to suspect there is more to Professor Laskey's party than initially appears...
The Doctor realises that if he can speed up the Vervoids life span with light, they will decay. Using vionesium, he does so, unwittingly causing genocide in the process...
The Vervoids begin to attack the crew and passengers, while someone kills a Mogarian who isn't really a Mogarian at all, but an old friend of the Doctor's...
The Commadore loses command of his ship as Bruchner takes over the bridge, intending to send the Hyperion III into the black hole of Tartarus to destroy the Vervoids forever.
