Doctor Who: The Visitation

The Fifth Doctor tries to take Tegan back to Heathrow Airport but the TARDIS arrives in the 17th century instead of the 20th. The time travellers find a space capsule has crash-landed nearby and that its alien occupants, three Terileptil prison escapees, intend to wipe out all indigenous life on Earth by releasing rats infected with an enhanced strain of the great plague. The creatures are also using a sophisticated android to strike terror into the local villagers. Aided by itinerant thespian Richard Mace, the Doctor tries to unravel the evil plot.