The Second Doctor is unable to find his recorder and mentally re-enters the Land of Fiction to search for it, where he meets Lemuel Gulliver once again. However, when "Gulliver" suddenly quotes dialogue from Gulliver's Travels that Dean Swift never wrote, the Doctor realises that this is in fact the Time LordGoth. The Doctor finds himself unable to wake up and is told by Goth that the Time Lords require his assistance urgently, showing an image of vital cosmic energy being drained away into a black hole. Next thing he knows, the Doctor finds himself in the TARDIS once again, face to face with both his next incarnation and future companion.
This story served as a prequel to The Three Doctors, explaining that the Second Doctor got recruited by the Time Lord into the fight against the anti-matter universe immediately after The Mind Robber. In an oversight, however, The Three Doctors makes explicate reference to The Invasion, despite the Doctor using his recorder to spy on Tobias Vaughn's base in that serial, which aired right after The Mind Robber, without explaining how the Doctor recovered his recorder after it was destroyed in Omega's anti-matter universe during The Three Doctors.