London Bridge is falling down, and it's not alone. The Thames River is a strip of mud choked with debris, Parliament is a wreck, and Big Ben looms alone over a shattered city. Fires burn perpetually amongst the rubble and the sky above is a pale green soup. The Hellgate has opened, and only a handful of humans survive in the demon-infested aftermath.

Fortunately, they have big guns. Lots of 'em.