This Is Not Heathrow!

At the manor house occupied by a 17th-century family, an unwelcome alien visitor arrives. A young girl, called Elizabeth, witnesses from a window strange lights in the sky. She goes to tell Squire John, Charles and their servant Ralph what she has seen. But unknown to all the occupants, of Squire John’s house, they are all about to be killed by a Terileptil.

Unaware of these events The Doctor is trying to return his travelling companion Tegan Jovanka to Heathrow in 1981, half an hour before she first entered the TARDIS. But the TARDIS is behaving erratically and The Doctor blames the fault on the lateral balance cones. The TARDIS therefore arrives at the right location but is some 300 years too early.

While investigating their surroundings The Doctor, Adric, Nyssa and Tegan, discover that members of a nearby village are burning potassium and sulphur in the woods to ward off the plague. The Doctor and his three travelling companions meet up with Richard Mace, an unemployed actor, who leads them to the safety of a barn. While there The Doctor notices an ornament made from polygrite around Richard Mace’s neck and recognises it as part of an alien bracelet from a prison planet. Then when Richard Mace speaks of a comet falling to Earth a few weeks earlier, The Doctor correctly surmises that this might have been a spaceship crashing and that there might be survivors. Lending weight to his theory, Nyssa then finds some power packs in the barn.

Adric, Tegan and Nyssa

The barn is owned by Squire John, and Richard Mace takes the travellers to the Squire’s house. The place however, is deserted. The Doctor decides to have a look around and finds a laser mark on a wall by some stairs, but the base of the staircase is apparently blocked by a brick wall. The Doctor realises that this wall is in fact an energy barrier. When he breaches it he recognises the smell of soliton gas. The travellers are then surprised by an arrival of an android, which renders Adric and Tegan unconscious. The Doctor, Nyssa and Richard Mace though manage to escape.

While the android takes Adric and Tegan to its master, the Terileptil, who then questions them, The Doctor suggests that a sonic booster and frequency modulator might vibrate the android to pieces. Meanwhile the Terileptil orders the local poacher and a group of villagers, all of whom are enslaved to his will by control bracelets worn on their wrists, to capture The Doctor and find the TARDIS.

Richard Mace

The Doctor, with Nyssa and Richard Mace, locate the crashed spaceship and discover that it is still operational. While investigating the Terileptil’s spaceship they come under attack from the controlled poacher, axeman and wood collector. After escaping Nyssa returns to the TARDIS, to construct the sonic device with which to attack the android, while The Doctor and Richard Mace go to see the miller. However, they discover that he too is under the Terileptil’s control and so they find themselves captured by the villagers and held in the barn.

Meanwhile the Terileptil fits Tegan with a control bracelet, but Adric manages to escape and he heads for the TARDIS. On learning of capture of The Doctor and Richard Mace, The Terileptil sends the android to bring them to the Squire’s house. The Terileptil then reveals that he and the others in his group are escapees from the Tinclavic mines on the planet Raaga. Terileptil law states that imprisonment on Raaga is for life, so The Doctor cannot return them home. Their spaceship was badly damaged in an asteroid storm, and all but four of them perished in the crash. One of the four who survived has also since died. The Doctor is horrified to discover that the Terileptil leader plans to try to wipe out humanity.

The Doctor and Richard Mace are then placed in a cell. However, when The Doctor attempts to escape from the cell using his sonic screwdriver, the Terileptil catches him and destroys The Doctor’s sonic screwdriver. The Terileptil then reveals that he plans to infect black rats with a genetically-engineered plague, intended to augment the Black Death that is already spreading across the country. When the Terileptil has gone, The Doctor manages to escape and he rescues Tegan and Richard Mace. They are unable to return to the TARDIS, however, as they find that all the exits from the house are sealed.

A Terileptil

Nyssa has meanwhile completed the sonic device, which proves its effectiveness after Adric inadvertently allows the android access to the TARDIS. Adric then pilots the TARDIS to the Squire’s house and rescues The Doctor’s party. They then all travel to London, following a trail of electrical emissions from the Terileptil’s equipment.

There they discover the Terileptil leader and the other surviving Terileptils using a small bakery as a base. Richard Mace despatches one of the creatures but, in the struggle, a flaming torch sets fire to the shop. In the heat the Terileptil leader’s gun then explodes and the remaining two Terileptils perish in the blaze. The Doctor, Richard Mace, Tegan, Nyssa and Adric then throw the plague serum into the fire – so ending the Terileptils’ plans.

With the fire starting to take hold of the properties around the bakery Richard Mace stays behind to fight the blaze as The Doctor and his three travelling companions enter the TARDIS. Tegan though is concerned about the fire that has broken out, but The Doctor knowingly comments they should let it run its course.

As the TARDIS dematerialises, a street sign reveals that the bakery is situated in Pudding Lane, the location where the Great Fire of London started.