Head out to the hallway and press the console which'll start a long cutscene.
Tiedemann's fat face will come spammail you, head on to the Store and purchase as much ammo and medkits as you can.
A lot of necromorphs will come after you in this room, use Stasis and preferably the Contact Beam's alternate fire.
Once all the necromorphs are dead head to the door and hack the terminal to open the door.
Once you walk down the hallway DO NOT AIM. DO NOT WALK TOWARDS THEM. DO NOT EVEN BLINK. DON'T BREATHE.
Simply head to the bathroom to your left, anything more will get you shot.
In the bathroom, get to the crawlspace and start crawling!
Once in the observing room, take out the power cell and then the soldiers will be completely SWARMED with necromorphs.
It's pretty scary to look at honestly, EA did a great job with these last chapters.
Head downstairs and prepare for a fight, some Infectors coupled with Slashers and lots of Pukers.
If you survive, head into the room. Nicole will allow you to use your Locator to find the Marker.
To get past the force field, take this guy's corpse and scan it.
Be careful unlocking doors, unless you're into this type of thing.
In this power closet is a LOT of goodies. I say open it!
The last divider in the game. Enjoy it while it lasts.
Isaac's into asphyxiation, don't worry.
Remember when I wrongfully predicted the last of Stalkers? I lied. This is the last place where you'll find stalkers, and they come with Pukers. Every monster you'll encounter is Enhanced from now on so I don't have to mention it.
If you kill the Stalkers, take the power cell from the ceiling and replace it with the one on the door here to progress.
To get past the laser room, first clear the necromorphs out then....
Stasis the laser that is heading TOWARDS you when you EXIT the door. Then HAUL ASS!
You'll make it to a lift, where you can power down the lasers and use kinesis to take down a bridge to get to the other side.
Keep heading forwards to the sound of horrific screams.
Closed stores make Isaac mad!
This next room is incredibly hard, so much that it won't be shamefur dispray if you lower your difficulty JUST because of this part. Exploders, pukers, and Spitting Enhanced Slashers all in one tiny room. That sound bad? Exploding babies are here too.
Keyword: Stasis. Also use Exploder arms to help out with the ones still alive.
There'll be another room just like this, and then you'll have to face a Brute.
Not JUST a brute though.
An ENHANCED BRUTE.
Stasis + contact beam completely nulls difficulty though, unless you've decided to play on Hardcore....
Keep moving, save, buy, and repair on the bench in this room.
Heading to the elevator will start a cutscene about the marker.
Then Isaac will head to this "Eye poke machine" and summarily give himself an eye exam.
Guide the laser EXTREMELY SLOWLY to Isaac's ever-dilating pupil, or the needle will jam into Isaac's face and that won't be fun.