"killing floor 2" is a first-person shooter video game that can be played alone or cooperatively with up to six players. the game is based on events from "killing floor", in which bio-tech firm horzine attempted to create military clones and was hijacked by an insane researcher who unleashed the clones across the uk. the clones have now rapidly spread across europe, paralyzing the response from the european union. in "killing floor 2", taking place a month after the first game, the outbreak has spread beyond europe, causing governments to collapse and communication systems to fail.