You're gonna start out in an elevator you finished the previous stage with, once it opens, a large room will be in front of you, but beware, imps and Vulgars immediately start attacking you without delay! Once they are finished off, head forward to the door in your view with green lights all over it, indicating it is unlocked. In this room, two galloping zombies attack you, kill them, and take a left down the corridor. Two imps will attack you as you approach the door, one from the door, the other from your right. Kill them, and go ahead to the next room.

A small stair-set will be at your left, go straight up it, you will see a chair and a few computers, then continue to the door now at your right. A cinematic will now play. Once it is finished, you find yourself in a new room with a key to the armory. Head up the stairs directly in front of you. You will soon encounter a zombie as you ascend. Kill him, and head to the next area.

This room contains a few Imps, a Vulgar, and a zombie, so keep your guard up. Below you will be a platform with computers, a health station, and some gear, collect it, and head to the next room.

Now you'll be in the room you started in, only now you are on a walkway looking over it on the 2nd story. A number of Vulgars attack you as you make your way down the path, keep going until you come to the door at the path's end. This room is in the shape of a 'U', ahead of you, an Imp spawns, kill him, and 2 more Vulgars will spawn, once the area is secured, continue to the next room.

Now you will be in a stairway, go down and kill the imp working it's way up to you, then Pick up the PDA on the bottom of the floor. Continue through the door. Now you'll be in a large area, kill all the Imps and Vulgars, and head to the access panel that reads: "Storage". Scan your PDA, and walk on through. Once again, you will be back in the room you started in, stay inside the rail guards, and advance up the pathway, killing a number of Imps along the way. Walk through the door at the opposite end of the path.

Does this area look familiar? Yep! Only now you have the key to the storage room! Go up to the access panel, scan the card, and Walk in. Kill the Vulgar that spawns ahead of you, and pick up the newly found Chaingun on the floor. ooooh... shiny.

Then go to the access panel that reads "Waste Tunnels", and activate it. Walk down this hall, and down the stairs, leading down to the double doors. Go through them, and a short cinematic plays. Once he puts on the helmet, your vision and hearing are a bit…distorted.

Now keep in mind... That radiation protection doesn’t last forever! So move quickly.

These tunnels are very straight-forward, and don't need a whole lot of brainpower to get through. Just keep pushing your way through, killing a wide variety of enemies until you come to the end of the final tunnel, where a double door exit is at your left. Now the marine will take the mask back off. Phew! that wasn’t easy...

Now head up the stairs ahead of you. Eventually coming to an airlock. Cycle it, and exit the airlock to Erebus Station.