The Doctor visits the home of Robert Stephenson who, on the eve of the industrial revolution, has called together a meeting of all the great minds of his age. Whilst there, the Doctor also discovers the Master, and an unscrupulous Time Lady known as the Rani - but why?
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Episode 1
Attracted to time turbulence, the Doctor and Peri arrive on early 19th
century Earth to discover a small mining community in turmoil. At first
it seems that a group of Luddites have taken over the area. The Doctor
investigates and finally tracks down the Rani, a renegade Time Lady,
who has taken over the local bath house and is draining the brains of
the miners of the chemical that induces natural sleep. Into the mixture
is thrown the Master. Forever out to cause trouble, he attempts to
humiliate and then kill the Doctor.

Episode 2
The Doctor is saved from a grim fate by inventor George Stephenson.
He and Peri return to Lord Ravensworth's, where Stephenson has
planned a meeting of scientific and engineering geniuses in the
village. Meanwhile, the Master has hatched a plan to speed up the
historical development of Earth so he can use it as a power base. His
plan involves using the minds of eminent scientists including
Stephenson, and he makes a deal with the Rani over her brain-fluid
project. Fortunately, the Doctor is able to resolve the situation, and
the Master and the Rani are sent spinning into time and space trapped
in a disabled Tardis.