OK, in essence your task is to run out the way you came in, but some doors are now blocked so you have to take different routes. You begin by heading into a room with a battle between the two factions of bad guys. Be warned that the zombie bad guys can jump UP so you're not safe on a higher ledge! Go out the side door.
In the next room, you have to jump up on the boxes to get up to the upper level and leave through there.
You're in the lightning room. Go down the lift. You find a room with a broken light bridge, and active camo to the right. Jump up the blocks again. In the room with the on-off bridge, keep straight. In the room with four screens, jump on block for healtha nd shotgun. Jump up higher to leave the room.
Cross the light bridge and take the lift up. You meet up with a group of marines. Run through the swamps with them, following the red beacons.
