The Sarah Jane Adventures - Season 3 Episode 6 -

Sarah Jane and Peter end up in a white room, a void where Peter tells her that he nearly died but the Trickster saved him and struck up a deal if he married Sarah Jane. He had no idea that any harm would be done to her or her friends. The Trickster explains his plan - to give Sarah Jane a new life so that she would forget her old one as a guardian of the Earth and make it vulnerable to the likes of him. The Doctor, K9, Rani and the boys have been trapped in a similar void but eventually make contact with Sarah Jane. Sadly, the only way for the Trickster to be defeated...