Danger Down Below ( short story ) Summary . The Doctor has landed on the planet Aronassus 49 in response to a general distress call from his old friend , High Minister Threll . He ' s not quite sure why Threll is in trouble , but their friendship makes answering the call a priority . After a long trek through the desert surrounding Prime City , the Doctor and Tegan finally are escorted roughly to Threll by the city ' s guards . Threll is considerably happier to see the Doctor than his guards were . He marvels for a moment at the Doctor ' s regenerative powers before explaining the problem . The city ' s food synthesisers are on the fritz , and the city ' s population has now begun to starve . Catastrophe is imminent , unless they can be repaired . Unfortunately , Threll has no idea what exactly is wrong with them , because he doesn ' t have clear access to them . The Doctor , naturally , wants to examine the problem up close . As the trio descend to the city ' s service areas , their progress is temporarily thwarted by Chief Guard Sholl , who wants to arrest Threll . Sholl alleges that Thrall is derelict in his duties , and has in some way exacerbated the conditions of the famine . He goes on to say that the penalty for these crimes is immediate death . Just at that moment , an electrically charged ball bounces into the area , touching all of the security guards . They are all instantly incapacitated . The Doctor surmises that the ball was a projection of a larger alien body down in the foot synthesiser area — a kind of defensive mechanism , much like the human body ' s white corpuscles , but more sentient . It realised that the guards were threatening Threll and the Doctor , whom it somehow sensed would be more sympathetic to its host . The trio continue to make progress towards the synthesisers . Once they arrive , they immediately see the problem . A giant creature has taken over the room and is consuming the food that the machines produce . The Doctor identifies it as a Mirator from the Andromeda Galaxy , and realised that he must somehow get the Migrator back into space . Its long journey from the Andromeda Galaxy to an uninhabited world was interrupted by the binary star system around this planet . The two hot suns awakened the creature prematurely from its state of suspended animation and forced it to land . If he can get it back into space , things will return to normal on Aronassus 49 . The Doctor rushes off to get the TARDIS , leaving Tegan and Threll to deal with the guards who have now awakened from the slumber caused by the Migrator ' s symbiotic " friends " . The energy balls leap back into action to help stave off the guards . In the midst of this fight , the TARDIS materialises and whisks the Migrator , Tegan and Threll away . The guards are left to find and begin to distribute whatever food the Migrator hasn ' t yet eaten . In space , the Doctor , Nyssa , Tegan and Threll manage to get the Migrator back in suspended animation so that it can complete its journey to an uninhabited world . The Doctor then proposes they have a big celebration . Threll is shocked ; surely it would be so unseemly so close to the near - starvation of his people . The Doctor agrees , but adds , " That ' s why being a Time Lord comes in so handy sometimes . " He can use the TARDIS to get Threll back home seven days in the future , by which time his people will regard Threll as a hero and a party " will " be in order . Notes . " to be added " Continuity . " to be added "