The Fifth Doctor tries to return Tegan to the Heathrow she left in 1981, but instead the TARDIS lands just outside London in 1666 – the year of the Great Plague.

The Doctor and his companions receive a decidedly cool welcome – and it soon becomes clear that the sinister activities of other visitors from space and time have made the villagers extremely sensitive of outsiders.

And as a result of the aliens’ evil schemes, the Doctor finds himself on the point of playing a key role in a gruesome historical event.