When the Doctor lands his TARDIS in the Lancashire town of Lannet in the present day, he finds that something is terribly wrong.
The people are scared. They don't like going out onto the streets at night, they don't like making too much noise, and they certainly don't like strangers asking too many questions. What alien force has invaded the town? Why is it watching barmaid Alison Cheney? And what plans does it have for the future of the planet Earth?
The Doctor is helped (and hindered) by his new military liaison, Major Kennet, and his Royal Green Jacket troop. His old enemy, the Master, also plays a small part.
During the course of this adventure, he encounters a brand new race of ferocious alien monsters and strikes up a friendship with his latest companion, Alison.
While starting with a small community under threat, this old-fashioned, very traditional but very up to date Doctor Who adventure takes in the entire world, from New Zealand to India, Siberia to the USA, and cosmic expanses beyond.