You have just been recuited to a secret military installation. You just get your duffle bag on your bunk when the CO calls you in and tells you about your first mission. You will be dropped into a control center that the demon pukes have invaded. You must clear the control center of all the baddies and turn the main generator back on. You try to tell your CO that you just got here, but he beats the crap out of you, dumps you in the plane and kicks you out of the plane, and through the roof of the building. You realize that you'll need to use every trick in the book to get past the demons and get the damned generator back on. You pick up Shotgun and carry out the mission.