The Doctor and Peri

Deflected off course, the TARDIS materialises in the north of England, near the village of Killingworth. The Doctor and his companion, Peri, have arrived in the Nineteenth Century at the dawn of the industrial revolution, a critical period in Earth's history. The introduction of machinery has met with much opposition from working people, some of whom have begun attacking and destroying it. But the Luddites around the village of Killingworth are strangely much more violent and active than anywhere else in the country.

The Doctor though is not the only alien visitor in Killingworth, nor is he the only Time Lord. His arch enemy The Master is plotting to use Earth as a base for his operations, and it is he who is responsible for diverting the TARDIS. There is also another Time Lord at work in the village. This is The Rani, an exile from Gallifrey and a brilliant biochemist.

Cast out from Gallifrey because of her dangerous and callous experiments, having caused mice to be turned into monsters which ate the President's pet cat and who then bit the President himself, The Rani has now become dictator of a planet called Miasimia Goria. There, she has altered the metabolism of the populace, heightening their awareness but also, as an unfortunate side-effect, lowering their ability to sleep. In order to correct this defect, she has been extracting a chemical from the brains of humans, unconcerned by the fact that this leaves the humans aggressive and unable to sleep themselves. She has been conducting this operation at various points throughout Earth's history, some of her previous visits having aggravated the Trojan Wars, the Dark Ages and the American War of Independence. Now she is adding to the unrest caused by the Luddites.

The Rani In Disguise

When The Rani discovers that both The Master and The Doctor have arrived, and so could risk her whole operation on Earth, she is less than happy. She initially refuses The Master's pleas to help him in his continuing attempts to kill The Doctor but is forced to change her mind when he steals a vial of precious brain fluid from her and uses it to blackmail her.

Lord Ravensworth, the owner of the mine in the village, has invited a number of the finest engineering geniuses - including Humphrey Davey, Thomas Telford, Michael Faraday, Mark Brunell and George Stephenson - to a meeting where they are to view George Stephenson's latest steam engine. The Master realises that, with the aid of some maggots which The Rani has chemically impregnated with an obedience-inducing drug, he can control these key figures in Earth's history and thereby change the future, ensuring that the Industrial Revolution never happens. But first he has to deal with The Doctor.

Meeting George Stephenson

First The Master arranges for a group of aggressive miners to push The Doctor’s TARDIS down a mineshaft. The Doctor meanwhile has dressed as a miner and infiltrated the bath-house that The Rani is using to extract the chemical from the brains of the miners. He soon deduces The Rani's schemes but she entraps him and straps The Doctor to a trolley. With the assistance of Peri he manages to escape even though he is still strapped to the trolley. But worse is to come when he is discovered by the group of aggressive miners who place The Doctor onto the top of a mine cart and then push him down a slope. The mine cart rattles along its rails, fast approaching the gaping entrance to the mineshaft...

Luckily The Doctor is rescued by George Stephenson, who is preparing for his meeting. Then using one of The Rani's maggots, The Master takes over George Stephenson's apprentice, Luke, and uses him to spy on The Doctor and George Stephenson. The Doctor meanwhile locates and enters The Rani’s TARDIS.

Operating her time-machine using a Stattenheim remote control, The Rani brings it into the mine where she and The Master are waiting. Unaware that The Doctor is hiding on board, and so can overhear them, they plot to set a trap for George Stephenson in Redfern Dell. When they have gone, The Doctor sabotages her TARDIS's navigational system and velocity regulator.

The Master

To make herself useful, and to make use of her botanical knowledge to make a sleeping draught for the afflicted miners, Peri has also gone to Redfern Dell. The Doctor arrives just in time to prevent her from suffering the same fate as Luke, who has stumbled on to one of The Rani's chemical land-mines and has been converted into a tree. The Doctor forces The Rani to lead Peri out of danger. However, once Peri has left to escort The Rani and The Master as prisoners back to The Rani's TARDIS, The Doctor is again captured by the aggressive miners. He is tied hand and foot to a pole, but manages to escape when the two miners who are carrying it simultaneously step on to landmines and become trees.

Following Peri to the mine, The Doctor finds that her prisoners have outwitted her and escaped. Inside the mine The Master fires his tissue compression eliminator at The Doctor but hits a support beam instead, causing the roof of the mine to collapse. The Doctor and Peri are forced to head for the exit while The Rani and The Master enter The Rani's TARDIS. However, affected by The Doctor's sabotage, The Rani's TARDIS spins out of control through the vortex. The resultant time spillage causes a tyrannosaurus rex embryo, collected by The Rani on an earlier visit to Earth, to crash to the floor. The Master and The Rani find themselves trapped against the TARDIS walls by the G-force and can only look on in horror as the dinosaur begins to grow.

With The Rani and The Master disposed of George Stephenson arranges for a group of men to get The Doctor's TARDIS out of the pit, and The Doctor and Peri give Lord Ravensworth a vial of the brain fluid, which The Doctor had retrieved from The Master, with instructions to administer it to the affected miners.

Then the TARDIS dematerialises leaving Lord Ravensworth and George Stephenson puzzled as to where The Doctor and Peri have gone.