- 1. You are now playing as Nathan McNeill. After the lengthy dialogue, Nathan will follow his crew out of command control, past a row of lockers. Note that all "openable" lockers here have a purplish light on them; open them to get P-Sec ammo. Don't miss the plasma cutter on top of the lockers, it may only be there if you replay the level since I don't remember seeing it on the first attempt.
- 2. Text Log #1: It's in the openable locker furthest to the left along the locker row. You have barely a chance to hit it before Nathan heads over to the exit door.
- 3. Nathan will walk down the next hall to an elevator. Grab some ammo to the left as you continue to the elevator into the next room.
- 4. In the next room, there will be loads of P-Sec ammo. You'll need it as there will be hordes of Possessed here. They can survive a couple headshots with the P-Sec, but it is still a good weapon to spam against them.
- 1. Grab all the goodies you can before Nathan enters a waiting room.
- 2. After the cutscene, kill the madman, then the two hostages-turned-Possessed after your friends leave.
- 3. Text Log #2: After killing the hostages, Nathan will curse and turn to the right. It will be right on the floor in plain sight.
- 4. After the weird cutscene, exit through the door Nathan's allies left through.
- 5. Right off the bat in the next hall, you're attacked by two Possessed. Kill them.
- 6. Weapon Upgrade #1: It's in this hall. You'll have plenty of chances to get it, but the earliest is before killing the first two Possessed.
- 7. Grab all the ammo and supplies you can as Nathan goes from door to door, killing the Possessed as they charge out. He'll eventually reach the exit on the other side of the hall.
- 8. Text Log #3: Immediately after opening this exit door to the next room, grab it right on the floor, right in front of you, before Nathan enters the room.
- 9. There will be a massive amount of Possessed in here, usually double-teaming you. Spam the P-Sec pistol if things get hectic as if they close in they will take up most of the screen, blocking your aim. When the action finally dies down, Nathan will escape.
- 10. Outside the clinic, Nathan will run through the crowd of Possessed and encounter Gabe. Shoot the rookie when he gets possessed; your group will then flee into the P-Sec Headquarters.
- 1. Nathan will grab a grate off the wall and slam it on the entrance door. Switch to the Rivet Gun and fire charged shots at each of the six blue markers on the grate to seal the door. If you fail to do this in time, you'll be killed and must retry.
- 2. Weapon Upgrade #2: You can see it briefly as Nathan turns towards Gabe before grabbing the grate. Although it's possible to get it later, it's best to get it then as if you miss, just fail the welding grate mini-game so you die and can try again for it.
- 3. Nathan will eventually enter an elevator; ride it up.
- 4. In the next room, you'll have to battle your first Slasher. You'll definitely want to shoot off their pincher-like arms as that does a lot of damage and makes them less dangerous. Shooting their bodies is mostly futile, and blowing off their heads will likely make them swing around in a frenzy, so watch it.
- 5. Afterward, you're back in the command control. There's plenty of Slashers in here; shoot them up.
- 6. After the lengthy dialogue, Nathan will head back out and ride an elevator outside downward. You will get to use Free Look again; quickly turn left to shoot a purple Fuse Box, opening up an armory. Nathan will enter it and grab a Pulse Rifle.
- 7. Nathan and his group will return to the P-Sec lobby. Shoot off each of the six weld spots on the grate you welded earlier to head outside.
- 8. Outside, you'll take on a couple of Infectors as well as Slashers. The Infectors can fly around and infect dead corpses to make Super Slashers, so target them first if possible.
- 9. Nathan's group continues to a wreckage that his allies try to move while he fights off a massive group of Slashers. Keep trying to hit their limbs, using Timed Reloads to reload quickly. If you are desperate, switch to another weapon asap.
- 1. As the group heads to Mission Square, the space shuttles outside will be destroyed. Nathan will then run into the square.
- 2. Weapon Upgrade #3: It's going to be on the left on the ground after the space shuttle destruction sequence, as Nathan enters the square. I believe you can get it again as Nathan fights off the horde attacking at the lift.
- 3. After the lengthy dialogue, grab the debris on the lift with the A button and fling them off with the B button. Doing so will cause a squad of Slashers and new enemies, "Leapers", to attack. The Leapers are faster and more deadly, so shoot them first.
- 4. Now you must finish a Hacking Mini-game...while under constant barrage from Leapers and Slashers. They will mostly come single-file, so distract them with a burst of Pulse Rifle fire, then work on the mini-game until it is complete.