[s5e11] The Lodger «FULL»

With the ship gone, the TARDIS is finally able to land. Craig and Sophie are finally a couple, and the Doctor departs, leaving them with a brand new set of keys—and a lot of stories to tell about their strange "lodger".

The story of (Series 5, Episode 11) is a unique "Doctor-lite" adventure where the Eleventh Doctor is forced to act like an ordinary human to solve a cosmic mystery. The Premise: Stuck on Earth [S5E11] The Lodger

The Doctor realizes that Craig is the key because he is the only person who want to leave; his love for Sophie and his life in Colchester provide the "grounding" the ship needs to shut down. With the ship gone, the TARDIS is finally able to land