Like many other entries on this list, this two-parter started off with a bang. The Tenth Doctor and Martha dash into the TARDIS, pursued by unknown adversaries. The Doctor then says a couple of mysterious lines about doing something that he has never done before, and then it cuts to a house in the countryside. The twist? The Doctor is no longer the Doctor, as he is instead a mild-mannered teacher by the name of John Smith. Martha appears to know what's really going on, but still plays along as a maid. It's a confounding start to the two-parter which sets up one of the most satisfying story climaxes in Doctor Who history.
