TV adaptation of the play set in a Cambridge School of English for Foreigners in 1962. St John Quartermaine is a rather ineffective but kindly teacher at the school who, becuase of his gentle character, has hardly any enemies - in fact, the rest of the staff confide in him or generally pplay on his good nature. Then Derek Meadle arrives on the scene. He is a new part-time teacher who really wants to be full-time, but people like Quartermaine are in the way.

Devon 1940. The boys of the local public school are alerted after a German parachute drop and as members of the Local Defence Volunteers they prepare to put their youthful enthusiasm for war into practice.

The Rani has returned with another malicious scientific scheme. Taking advantage of the post-regenerative trauma the recently regenerated and unstable Doctor is going through, she hopes to achieve control of an approaching asteroid composed entirely of strange matter. Can the Doctor figure out he is being used for the Rani's evil experiment, and what is behind the door the Rani won't allow him past?