Jon Pertwee was the third actor to play Doctor Who, and stars here in an episode that first aired in 1970. The Doctor and his fellow travellers aboard the Tardis have been thrown into a parallel universe where familiar characters emerge with different personality traits--a fascinating premise for one of the best ever episodes of the show.
Description by Warner Home Video:
Doctor Who: Ep. 54 - Inferno
An unsuccessful trial run with the Tardis console throws the Doctor into a parallel universe where his old friends are rather nasty characters.