Plot? Its supposed to be a stand-alone Fright Fest FPS. Does TF2 have a plot? Does Counter-Strike? Its not a single-player game with a plot. You are one of 4 generic survivors in some sort of viral outbreak (a la Raccoon City kinda thing) and your mission is to get through the maps to the end helicopter alive. I really hope you don't expect a plot, you are just setting yourself up for disappointment.
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