London, December 24th 1930, and notorious inventor Harry Grendelson is out on Hampstead Heath giving a public demonstration of his latest contraption, the Illumination, which he claims will amaze and astound the assembled crowd.
At the stroke of midnight, Grendleson shines a light into the night sky from his beacon-like contraption and the crowd gasp as a glowing ball of light crackles above them surrounded by a nimbus of lightning that arcs violently to and fro until, without warming, there is a panicked cry from the inventor as a bolt lashes out towards him to strike his machine which explodes. Thirty people were killed in the blast on Hampstead Heath that night, including Harry Gredelson himself. Yet, somehow, that was not the worst of it.
In place of the glowing light hung an eerie jagged swirling pattern that hurts the eyes to view like a crack in reality itself. Some swore that they could feel the pattern watching them and that they could hear strange whispers in their minds. The pattern sat in the sky above the heath and slowly day by day it was getting bigger.
Now visible beyond the pattern a strange alien city can be seen, a metropolis of dark twisting streets and derelict buildings that vanish away into the darkness. Crawling amid the cracked paving slabs and rubble are things too horrible and blasphemous to contemplate – thongs that are breaking through the crack seeking sustenance.
So far the assembled garrison of soldiers that has cordoned off the area can deal with the small creatures that have slithered through but how long until something larger attacks?
Somehow the breach must be closed.