The story is set in 19th century England. The Master is plotting to kill some of the key figures of the Industrial Revolution and the Rani is stealing brain chemicals from humans to help her keep control of the population of the planet she rules.
The story was written by Pip and Jane Baker and directed by Sarah Hellings. The cast also includes Terence Alexander (Lord Ravensworth) and Gary Cady (Luke Ward).
See also List of Doctor Who serials