Part 49

Exit the lift and use the hornet gun to open the doors. Fire hornets at a spot beneath the large lambda symbol on the orange sign to hit an unseen vortigaunt.

Move to the back of the lift with the assault rifle. If the vortigaunt appears in the passage to the right, shoot it.

If the vortigaunt moves to the left near an explosive crate, move close to the lift doorway and fire hornets to the left to make it move into the hallway. Peek out and use altfire hornets to blow up the crate, killing the vortigaunt.

In the hallway, approach the entrance slowly until you see the two remaining vortigaunts. Use the shotgun to quickly kill them with a double-barrel blast, strafing for cover. Use the explosive crate to help.

Go to the back of the hallway where it splits. Prepare the hornet gun for three sets of teleport-in aliens.

The first set may have already teleported in. Go along the left edge of the hallway until you see a vortigaunt on a walkway to the right. Let it see you, hit it with hornets, then back up and shoot it in the head with the assault rifle.

Move along the left side of the hall until you see the blue "01 COOLANT REACTOR" sign. Fire hornets toward the sign to hit an alien grunt.

Return to the hallway intersection and turn right. Pass a security guard, go down stairs, and through a door to find a room with rechargers and ammo.

Return to the hallway split and go down the other way. Run to the end of that hallway without opening the door, then return to the T-intersection. This should trigger the second pair of teleport-in aliens. Repeat the process of killing the vortigaunt and then the grunt.

If the third pair doesn't appear, go to where the vortigaunts appear, then down the ramp to a hallway with red machinery. Run back and forth to trigger the final teleport-in aliens. Sneak-shoot them from near the bottom of the ramps. Repeat hallway running if necessary.

Get the security guard to follow you. Follow the blue "01 COOLANT SYSTEM" signs to a spot with two dead scientists.

Move past the scientists; a vortigaunt will teleport in. Position yourself so the security guard is between you and the vortigaunt. After the guard is zapped, shoot the vortigaunt with altfire hornets. If the guard survives, whack him for ammo. Alternatively, use a C4 satchel bomb.

Move to the door at the end of the hall to open it. Fire hornets toward the left side of the room beyond to kill the three alien grunts before entering.

Climb the ladder to the upper walkway, go along it to a door, then up stairs to the pump room.

Use hornets to kill the nearby headcrab. Move forward to kill another headcrab on the lower floor to the right of the big blue pump machine.

Move to the walkway split, then retreat to the corner by the stairs. Wait for two vorts to teleport in.

Use hornets to sneak-shoot the vortigaunt on the upper walkway to the right.

Crouch-walk along the walkway until you can use the crossbow to sneak-shoot the vortigaunt on the other side of the pump machine.

Move along the side walkway and examine the pump machine with the flashlight until you see its red lever. Quicksave.

Drop off the walkway at the spot nearest the red lever, use it, and run for the ladder back to the walkway. Two more vorts will teleport in; leave the area quickly if you are fast enough.

Make your way back to the hall.