After looting all of the Intel from Birkin’s lab, you will be ready to head into the next section, and the next combat encounter. Open the sliding glass door at the back of the room, near the Laptop, and follow HUNK. He will enter the lab at the end of the hallway along with a nameless squad member to confront Birkin, leaving you and your squad outside to cover him. At first, nothing will happen, although you will be able to hear the chaos inside of the lab. During this brief period of peace, search above the door to find another Security Camera that you should shoot.
You may see the imminent enemy attack coming, but there will be nothing you can do about it. Don’t even bother taking cover, as the door at the far end of the hallway will explode and you will all be thrown to the ground, cover or no cover. Get up quickly and take cover behind the small block protruding out from the left side. Shoot the two or three enemies who are brave enough to stand in the entryway to the lab, and then follow your squad outside to clean up the remaining enemies in the larger room. There will be a fairly large number of enemies in this room taking cover behind the various crates towards the back of the area. Take cover behind one of the crates yourself and fire back at them. Take them one at a time from a medium distance to keep yourself relatively safe. Just watch out for the enemies throwing grenades, which they will occasionally do to flush you out. When you see a red indicator on your screen, roll in the opposite direction and quickly establish a new cover position.
If you have a Shotgun, you can also rush straight at the enemies instead of holing up behind cover. In this case, you should sprint straight out of the small hallway that you started in and rush to the right. Take out the enemy cowering behind cover to the right first, and then quickly turn your attention to the crates to the left to find two more enemies hiding. Take them out the same way. If any of them get too close, hit them with melee to knock them back, giving you a chance to finish them off with a gory Shotgun blast.
A third way to approach this situation is to flush the enemy forces out of cover using explosives. This strategy works best if you are playing the Demolitions class, as they come equipped with explosives and armor that will protect them from the resulting explosions, but any class should have picked up a decent amount of grenades by now. Toss a Frag Grenade right in the middle of the cluster of crates to drive the enemies out, killing those who aren’t fast enough. When they are flushed from cover, pop out from your own cover and mow them down.
After you kill all of the enemies in this area, take cover, as more troops will rush in from the back. Depending on the strategy you used during the last battle, you can use various tactics to defeat this next wave. If you chose to hang back and pick the enemies off at medium range, you can stick to that strategy here with relative success. You may need to toss a grenade over to cover your left flank, though, as there won’t be much in the way of protection over there. If you chose to rush forward with a Shotgun, you will already be in close proximity to the enemies when they enter the area. Try to reload before they can get into the room, if you can. Otherwise, you will have to take cover on the side of one of the crates while you reload. When the enemies get close, blow them to bits with the Shotgun, or take them out with melee attacks. Keep a careful eye on your health, though, as it can be easy to die without even realizing that you were low on health in the first place. If the enemies start doing too much damage, retreat to the cover in the center of the room, directly in front of the entrance to the small hallway where you began this battle, and take out your Pistol to pick off the enemies from medium distance. You can adopt a similar strategy if you chose to toss all of your grenades at the last wave of enemies. Either head in close to kill with a Shotgun and melee attacks, or retreat to a distance and attack with a Rifle, depending on which you brought into the level. No matter what strategy you chose earlier, if you still have any grenades, toss one or two into the doorway that the enemies are rushing out of. If you are lucky, you might be able to kill a large number of this second wave before they can deal any damage to you.
After the second wave is done with, search the area to find a few collectibles. First off is the Intel sitting on the crate inside of the entrance that the enemies poured through. When you have picked this up, look up to the wall to find a Security Camera that you can shoot down. Finally, head all the way down to the end of the room and search to the left to find First Aid Spray, a Frag Grenade, and an Incendiary Grenade. If you need ammo, search the area, especially the floor. You may find little stashes of ammo on the ground, if you haven’t had to pick any of them up already. Once you have collected all of these items, it is safe to meet back up with HUNK. Head back down the corridor to find him, along with the rest of your squad, waiting for you on a lift. Be sure that you are ready for some serious combat now, as you will have to face a large, mutated version of Birkin during the next checkpoint. When you are ready to go, get onto the lift with the rest of your squad and ride it down.