When the mission starts Kelly calls you again and nags about the transmission. Ok so proceed into the garage and pick up some shards on top of the crate. Meanwhile a cacodemon will appear. Its good to take them down CLOSE with a shotgun before they get a chance. Now crawl into a vent in the southern corner of the room. In there you will find armour, cells, and a clip down the ladder. When you come back out of the vent you will be greeted by two imps. After they are dead go under the stairs to pick up some more armour. There is a health station up the stairs. Use it. Go to the elevator across the catwalk and kill the cacodemon. Call the elevator and bring it to Satellite Control.

When out of the elevator kill the machinegun zombie in the hole in the wall. To the right of the elevator is a panel. Activate it to open the hatch. Go back south till you get to a red door an imp will appear behind the door. Kill it and enter the hatch on the door's left. An imp will be near the elevator. Kill it and then take the med kit and armour near you. Go back then through the red door to a windowed hallway.

The light flicker and turn off as you go but don't worry. When in the next room there are two solder zombies near that control area. Pick up the clip and armour and then activate the panel which unlocks the Communications area. When you do this a cacodemon will attack you. Also two solder zombies will run into the room and attack. Now go through the door you just unlocked and use the health station if you need it. Go through the door to the west to a hallway.

When you enter the hallway you will see Campbell blowing up the communications with his BFG (Big ------- Gun). Go through the door at the other end and kill the zombie that attacks you. Take good aim for this zombie has a shield. Also kill the shotgun zombie behind you. At the bottom of the stairs is a door that leads to a PDA. Science the BFG toasted the electronics, Kelly tells you too the Satellite Control Center. Go back to the hallway and kill the shield zombie and enter the door you haven't gone in yet. Before you enter an opening in the wall will have a zombie and supplies in it. Once you pick them up kill the imp that appears. Then go to the engineering room.

Kill the zombie to the left and pick up the cells and armour. Next go through the door in the west side of the room. In this room there will be an imp and two zombies. Then pick up the med kit and clip in this room. Use the panel to call the lift. When you ride the lift down kill the fat zombie and the imp that await you. In the corner of the room are some grenades, health, and armour. Go through the northern door. In there is a solder zombie and an imp above. Get the med kit and clip and proceed to next room. There is an imp to your left and a zombie to your right. Take out the imp first for it's only a fat zombie. There is an ammo belt where the fat zombie was. Use the panel to open a vent that will have some goodies in it. When done come back out and go down the stairs. There are some supplies in the corner of this room. When you pick them up go back to the stairs to kill the three imps that appeared. Go to the red door and kill the 2 imps that attack you. In this next room kill the fat zombie. When you pick up the med kit in the center kill the imp that attacks you. In the next room kill the zombie and jump on the barrels to get yourself on the catwalk above. There is some good stuff on the floor and on the catwalk. Go to the end door to get cells and kill the imps near you then go south to the next part of engineering. At the other room's end there is an imp needing a nice can of bullets. Kill the shotgun zombie near the middle of the room. Get some ammo and armour on the ground before going up the stairs. Go through the door at the end and avoid the moving parts (they will hurt you). Pick up the med kit in this room and kill the imp that appears. Then ride the lift to the upper level. Kill the imp in the upper level and go through the eastern door. Now go up more stairs and kill the two solder zombies that you see. Go to the are below to pick up some essentials and Ben Wolfe's PDA which says locker #054's code is 246. Go thought the door you now have access to and kill the two cacodemons and the zombie that will attack you. Go through the unlocked door.

Kill the machinegun zombie in the office area and type 246 in the locker to get grenades and armour. There are more grenades and cells on a desk near you. When you get to the main console Kelly tells you where the invasion is coming from. Touch the near panel to start up the handy sentry bot. Just keep following it. It will kill everything it sees. The bot will leave you to kill two cacodemons. When you have done so go into the Thermal Control room.

Near the crate near the entrance is a med kit and a clip. As you follow the bot kill a cacodemon that appears behind you as it will kill and imp. When you get to the elevator ride it up to level 3. Kelly will tell you that Swann is nearby. Pick up the PDA outside of the level 3 elevator. Keep going forward into the skyway. And then into the Satellite Control room. Approach the objective point and them watch what is said on the screen. Pick what ever you think is best. It WONT affect the ending of the game.

Now go back to the elevator and go down to level 1. When it opens kill the zombie to the left and the imp .In the west you will kill another imp. Go through the next door. Keep dodging the imps fireballs as you take out the zombie first for he doesn't miss. In the south of the hallway kill the shotgun zombie and use the health station if needed. Also pick up the grenades and shotgun ammo. Kill the imp that jumps out at you. Go back up the elevator to level 3. Backtrack on level 3 till you get to the door the WAS locked. Click the panel to go to the Monorail Skybridge to move onto Recycling Center 1.