During the level where you start with no weapons, go toward the spark and fix the junction box. Open the door where the walker is located, run behind the table, and wait for him. Run out where he was and close the door. He will be trapped in there for now. Get the ammo near the dead body and go to where the medic is located. Note: Do not turn on the switch on the side of the camera. Give him the ammo and have him follow you. Go down the hallway. There will be an explosion, but it will not hurt you. Go past it, then go forward until you see the man. Do not open the door. Fix the junction box and open the door to the left. Save and get the medi packs in the room. Have your man stay there and close him in. Go back to where you trapped the walker and open the door. Run to where you found the medic and have him come in. Then, go past him and look at him just inside the door. Just as he attacks, go back, strafe right, and lock him in. Go back to your man and he will heal you. Have him follow you. Go back in the room with the "probe table" and open the other door. Two scuttlers will attack, but your medic will kill them. Take your medic outside the door by the walker who is trapped. Have him stay there, then go back and open the big door. You will see big experiments everywhere, but there will be an injured man in the back. Heal him, then run to your medic. Close the door and make sure your men are with you. Have him fix the junction box that goes to the armory. A few Scuttlers will attack, but just go in and get equipped. Give one man a pistol, some ammunition to your medic, and ammunition, a medi pack, and flamethrower for yourself. Go to the man you saw behind the door. Take out your machine gun and open the door. Shoot him until the aim turns red, then change to flamethrower and burn him. Then, go in. You need to go to the room to the left and hit the first switch and the last switch. Then, go through into the room. There will be some Scuttlers here. Kill them all, then open Cell 6. Only have him come with you. Go back to the save room and save the game, then go past the save room to the door that will not work. Have your men stay there. Go to Cell 3 and look in the back. There is a vent. Shoot it open in first person mode. Crawl through, and on the other side, walk across. There will be two flame grenades. Pick them up. Look down to see two walkers. Jump past them and run to the door on the left behind the wall thing. Have your men follow you. Take out the flamethrower and kill the walkers. Note: Save the flame grenades, as they help at the next Boss. Afterthey are dead, head in and have your engineer fix the junction box. Get on the computer and get the code for the elevator. The elevator is where the man transformed at. Note: Go to the armory and stock up on ammunition; do not forget the tazer.