Interval 03 - Escalation
Objective: Locate and Kill Paxton Fettel
Although you just got blown to smithereens and knocked right through a reinforced plate glass window, you're apparently all right. You just got the wind knocked out of you. It's up to you to find and kill Fettel, now that Jankowski's disappeared.
To get past the first little puzzle here, enter the control room and flip the switch to rotate the walkway, then find the accessible end and walk across. You'll see Alma in the sewers here, but she's a crafty little girl, so you won't get a good look at her. You will get a good look at the Health Booster nearby, though.
Shortly after killing the next few soldiers, you'll come to another seeming dead end, but if you poke around near the storage tanks, you'll see a shootable padlock on a door. Blow it and climb up and over to move on.
From here on in, you'll have a few heavy fights to deal with, but nothing extremely complex. Just keep your head down, lean around corners to fire, and you should be all right.
Heavy Resistance
Eventually, you'll fall down into another set of sewers and go through a small loading screen. Some of the Intervals are big enough to justify splitting the level up into two smaller levels, so, enjoy the loading time, then get back to work.
This level doesn't have much in the way of challenging puzzles; it's just a series of firefights, albeit entertaining ones. When you reach the exterior portion of the level, with all the walkways and the empty holding tanks, be on the lookout for dropped shotguns, which you can exchange your pistols for. Near it, you can dive into a deep pit to find a Reflex Booster.
Beyond that area, you'll come to a broken bridge; to get past it, hop over the railing nearby and spin the wheel over the pit to fill the bridge area with water, which will also cause a couple of boxes to float to the top of the water. Jump across them to put your shotgun to good use, as there are more soldiers waiting for you.
Heavy Resistance, Continued
Soon after this little fight, you'll come across your first Proximity Mines, which will lead you into another portion of the demo level. With your shotgun, you can hop up onto the bench where the mines are, shoot one of the soldiers here, then wait for the rest to come to you while you blast them with your boomgun one by one.
If you recall the next little sequence from the demo, then you'll be well prepared for what happens next; when you try to cross a little wooden bridge to reach a door, a heavily (heavily!) armored opponent pops out with a 10mm HV Penetrator and will proceed to mess you up but good. We generally liked to throw a Proximity Mine at him as soon as he busts the door open, then retreat a bit and use our shotgun on him from medium distance, with slomo time allowing us to avoid his rounds somewhat. He's a tough foe, so be sure to have your health as high as possible before approaching the door.
Just after this fight, you'll note that the remaining Replica forces are pulling out of the area. When you spot two of them running away from you, look straight down to find another Health Booster; you'll need to jump the railing to get to it. After that, you'll come to a room which is seemingly unpassable; flip the wheel, though, to raise the water, and you'll be able to swim across to another area. The ladder leads to another dead end, but if you shoot the panel in the floor you'll access the crawlspace below.
Bad Water
Another sub-level. If you hop into the waterway under the bridge near the beginning of this area, you'll notice a glowing Health Booster; to reach it, you'll need to head down the nearby hallway, drop into another empty sewer, and walk back down the corridor to nab the health bonus.
After more firefights and general spookiness, you'll come to Mr. Moony, whom Fettel was interrogating before. He's not exactly good at finishing people off, though, as Moony will still be alive when you reach him; alive enough to mutter some cryptic words, at any rate. After Betters gets done yapping at you, you'll be ambushed by more soldiers, so be quick with the slomo key.
Eventually you'll reach a narrow corridor where gas is gushing out of a leaky pipe. If you shoot the pipe here, flames will billow out, damaging nearby opponents. From here, you can either just move up by walking up the steps, or you can take a longer path by heading into the nearby corridor, climbing up the ladder, and hitting the grate to open access to a crawlspace. After crawling through and jumping over some pipes, you'll reach a small space above the flames, where you'll find some Remote Bombs and a Reflex Booster. From there, it's just one more big fight until you reach the next sub-level.
Exeunt Omnes
The title of this subchapter means "everyone leaves," in case you were wondering. After climbing the ladder near where you begin, walk back down to the hallway where the soldier was placing proximity mines. You can shoot them, if you wish, but doing so will cause electrical arcing, which will still prevent you from getting past. Bust out the grate to your left to pass by this area.
After your first encounter with the soldiers here, you're going to find two ladders, one in an area partially submerged in water, and another one near a pair of rotary controls, on a walkway. If you walk up the ladder by the walkway, you can eventually reach an office with a Health Booster in it; the other ladder is the one that leads on. Flip the switch to disengage the electricity and off you go!
Be sure to bust through the locked door in the next hallway to access more grenades and an ASP Rifle, which essentially acts as a sniper rifle, should you desire one, scope and all. The next couple of sections are straight from the demo, so proceed slowly, kill anything that moves, and you should be all right.
After defeating the soldiers that drop from the helicopter, you'll come across a room filled with explosive barrels. Walking into the room will cause all manner of hell to break loose due to the scripted appearance of the soldiers here, so drop back to the entry hallway and wait for as many of them to come to you as possible. When their numbers have thinned out a bit, walk around the corner and start busting the remainder up. Watch out for one of the heavily-armored soldiers to appear from an upper doorway when you walk up the stairs, though.
When you reach the landing zone, kill everyone in the area to clear a path for your chopper to arrive. The most difficult foe here is another of the armored bastards. If you stay far enough away from him, though, you should be able to avoid the bulk of his fire, so just stay back and pop him with any accurate weapons you might be holding.