From the Introduction:
The Hive is a game set in a world that has been taken over by mobs under the control of an alien mind.
Sometime in the late 1960s, London Transport undercovered an alien spacecraft while excavating an extension at the Hobs Lane underground station. There was a lot of publicity about the discovery of Martians in London. However, it ended when a force in the craft awakened. The force took over the minds of those nearby, and welded them into a mob dedicated to killing any who would not join them.
The mob had strange psychic powers that they grew as more joined them. Only a few were immune. The influence of the mobs grew, until no place on Earth was safe. Then, they set about rebuilding the Earth in the image of their masters.
A few of the immune have survived.