Huge rooms with poisonous fog inhabited by giant sleepers await you here, but the worst part is the lack of gear. With that in mind, here's the loadout that took us to victory: DL (dmr/sniper/mines), Jim (dmr/combat shotty/cfoam), Me (autopistol/machine gun/cfoam). Yep, that second cfoam is imporant!
The first objective is to plug three power cells that came down with you into their respective generators so remember to bring them with you out of that room. There's a handy terminal near the start too which you can use to ping stuff and Jim has actually advances to writing things down in a notebook per run. Important things to find are the keys and the fog turbine.
Easy tip to getting past the first door: jump and stand ON the lock, then use a hammer to simply break the door. As long as your head is above the gas, you won't get infected. Go through and there should be a ladder to your left to get out of the fog.
Now this whole bit of putting the cells is pure stealth and for practice I could actually do it solo. That means there should be no reason to fight anything at this point (still stealth bop little guys if needed), though you might need to go back and forth a bit depending where the keys spawn. A cakewalk after sneaking past that mother in R4C2. For this walk through we'll pretend you got everything in the first room (which never happens).
From that ladder you will spot a key-locked security door. Once you have the key it will open with no alarm, but the room beyond is dark, always populated, and has those ugly screaming sacs on the walls and ceiling (which can be subdued using your flash light).
Carrying one cell I went in solo and followed the right wall eventually there's a small door to go through then turn right. There's good odds the generator required is in that corner. If there's a giant in the way, remember you can actually flank around and get to the generator from the other side - though it requires a quiet jump. Get out of there and that's one done.
Note: there is a second door from that initial dark chamber which you'll need to visit if the generator isn't in this room. Don't freak out if you goof up. I did on my way out and we had to fight the room, yet we still had enough gear to win the mission. Use the space provided to gun em down. :)
To find the second generator you simply need to explore to the North. It won't be in the fog nor will it be up any stairs. This is the easiest one to find/do. You also need to find the fog repeller and bulkhead key anyway. If you keep going North you will reach a darkish room that opens up to a "courtyard with balconies" sort of deal. The doors to the left hold both the bulkhead controls and a terminal to help ping stuff.
Once you find the bulkhead key, plug it in and choose the normal mission then head North again to find the actual non-alarmed bulkhead door. Things you need to bring here are a cell and the fog turbine. Ideally you've loaded up on fog repellers too as you will need them.
Go slow and follow the right wall, up the stairs and down the other side - you will find a big door to go through so do so and shut it behind you. The last generator is in here somewhere (usually to the right of the door). Find it, plug in the cell and now the fun part. Clear this room of all enemies as quietly as you can! Use repellers as needed if you need the fog turbine carrier to drop it for hammer use instead.
You need this clear as to reach the forward extraction you have to do the class III alarm door in this room! Once done, set mines and cfoam the door. Also put a fog repeller so that door-duty guy (in this case Jim) can focus on icing the door while everyone else does circles. He managed to hold it until all were done and then it was simply a matter of shooting well. I did toss a few more repellers to keep line of sight though.
Do the next zones as normal and avoid the scout if you can. Your last challenge will come from an Alarm IV blood door. If you've shut all the doors on the way in, there is only one the swarm will try enter from - the one nearest the blood door so Jim was on cfoam duty again, calling out when he ran low to swap with me. Some of those circles drop into the fog so again, repellers are handy. Obviously DL mined the door too and again all circles were done before the door broke.
Once done just hold the furthest space opposite the door. None of the scum even made it to us. Use everything left for the blood door and hold the corridor the scum came from next, as there are a pair of hybrid shooters in the mix that will come out. For some reason, there was also a pair of giants still sleeping in the final room that we killed just in case.
Anyway, the forward extraction circle is right here and it's a fast one to complete. Basically if you've made it here, you've already won.
