Part 10

From a wall niche, kill any enemies inside before proceeding.

Move along beams to enter another vent shaft by bashing its grate.

At the end of the shaft, look into the room and shoot the headcrab.

Crouch-hop over beams and walk on weak ceiling tiles to drop into a secret ammo room.

Take needed supplies, then open the room's door and go left to return to the security guard's location.

Go down the large ramp near the guard and turn right. Do not approach the lower room with crates and barrels yet.

Stay back and destroy the middle crate with your pistol to safely shoot the bullsquid behind the crates.

Go down to the lower room and collect grenades and shells.

Push two barrels up to the yellow floor line to mostly block the path.

Move a short distance past the yellow line to trigger two vortigaunts to teleport in.

Quickly get behind the barrels and shoot the vortigaunts over them.

Go back up the ramp and have the security guard follow you.

Proceed past the secret supply room's open door into a large cafeteria room with a zombie.

Toss a hand grenade at the zombie, then help your security guard kill it and any headcrabs that fall into the room.

At the back of the cafeteria, bash boards off a doorway with the crowbar.

Go down the hallway until section c1a2c loads.

Optional Skip: Lead your guard down the short hallway to the left of the cafeteria that ends in a locked door. Nudge him until he opens the door, then go through to bypass section c1a2c. Note that the guard and zombie that would have been present on the long route will be missing.

Around the corner is a room with two zombies feasting on dead scientists. Leave your security guard behind before entering this room.

Toss a grenade at the zombies and finish any survivors with the shotgun.

Retrieve your security guard and have him follow you again.

Use the large lever to the left of the big door near the zombie area.

Run through far enough for your security guard to follow before the door closes. If he doesn't make it, you can use the lever from the right side of the door to open it.

In the meat locker area's first room, go through the large open doors and turn right.

Let the headcrab around the corner see you, then retreat so your guard will shoot it.

Bash your way past the hanging meat.

Look through another large set of open doors to find a headcrab on the floor and one on a high shelf to the left. Shoot them or let your guard do it.

In the large room with three hanging pieces of meat, shoot the headcrab nearby.

A bullsquid is hiding behind some crates past the headcrab. Move to the left end of the black-and-yellow strip in the big doorway, turn on your flashlight, and scan the crates until you see a leg. Shoot the leg until the bullsquid dies.

Move into the bullsquid's area and look for another headcrab nearby.

Find the big red-lit switch on the wall and use it.

Move down the hallway and turn right to enter the back rooms.

A scientist will start running, chased by a bullsquid. Help your security guard take down the bullsquid.

Whack the scientist for ammo.

Look back in the room the bullsquid started in to find bullets and grenades on the floor next to dead bodies.

Return to the starting room and climb the short ladder to get onto a shelf.

At the other end of the shelf, break the vent grating and jump-crouch into the vent shaft.

Break out the other end of the vent shaft and follow the shelves until you reach a moving platform.

Board the moving platform when it passes and break its crates open for armor batteries.

When the platform moves past the vent opening across from where you boarded, get off.

With your flashlight on, move down the vent shaft until you are near a spot where it drops to a lower cross-shaft.

A headcrab will jump up from the lower shaft as you approach; it should miss you.

Carefully edge forward to sneak-shoot the headcrab.