Part 43

Jump onto the railing and then over the large walkway gap. Turn left to find a first aid station, then proceed until a grunt throws a marine through a wall.

Sneak-shoot the grunt through the wall hole with hornets, switching to the crossbow or gauss gun if it enters your line of sight.

Stand in the doorway to the right of the wall hole and look left to see a large floor hole. Shoot hornets into the hole until they stop swerving downward, targeting the two marines below.

Go to the large wall hole past the floor hole and look down to see a marine fighting an alien grunt. Immediately fire hornets at the grunt to eliminate it quickly.

Use altfire hornets to kill the marine visible on a rooftop further past the grunt.

Look up and fire hornets at the ceiling directly above you to hit a grunt before it moves.

Go to the edge of the large floor hole and destroy the biggest wooden crate with altfire hornets.

Crouch-drop onto the nearest small crate, then bash all three crates to find a health pack.

Find the large ramp leading to two short sandbag walls. Before ascending, go down the narrow alley to its left with your shotgun ready to confront a vortigaunt hiding around the corner.

After defeating the vortigaunt, go up the large ramp and turn around to see a high-up alien grunt. Shoot it with hornets. If it's not visible, move past the ramp's top and jump to get its attention.

Go back down the ramp and turn right. Pass an alien whoosh-thing on the ground and proceed to a small security booth. Pick up a shotgun from a shelf.

Return to the whoosh-thing and use it to get onto the nearby rooftop, aiming for the large square vent to avoid damage.

Bash and drop through a grating near the vent. Crouch-hop out of the water into a large metal pipe.

Equip the crossbow, quicksave, and enter zoom mode. Move down the pipe, aiming slightly right of the center of the round hatch door ahead. When a marine opens the door, shoot him in the head for a one-shot kill. If you miss, quickrestore and try again. (You may need two darts.)

Immediately after the marine is dead, move backward and crouch at the bottom of the water as the bomb in the pipe explodes overhead.

Once the flames disperse, crouch-hop back into the pipe and proceed to its other end. Push open the hatch door and drop into the room beyond.

Go around the corner into another room, then retreat until the sounds of marines fighting headcrabs cease.

Equip the hornet gun and slowly enter the room, sneak-shooting survivors with hornets. If marines are still alive, switch to the assault rifle to finish them.

When you reach a ladder going down, use it and check the alcove near the first aid station for any hidden enemies.

From the walkway near the top of the ladder, jump onto the railing and then onto the pipe leading to a large hatch door. Use the wheel to open it, which may cause you to fall. Climb back up and jump to the pipe again.

Crouch-walk through the open hatch door, ascend a short ladder, and follow the large pipe to its end.

As you near the end, equip the .357 and carefully move to shoot the marine at the bottom of the stairs to the right. If he spots you, shoot him down quickly. If he runs past, finish him before he reaches the stairs and kills an essential security guard.

Go to the bottom of the stairs to find a room with a locked door and a marine hiding behind shelves. Sneak-shoot him if necessary, and use the first aid station nearby.

Go to the top of the stairs to find the security guard. After he holsters his weapon, have him follow you to the locked door.

Once the security guard unlocks the door, leave him and proceed down the winding hallway.

You will emerge behind the short sandbag walls near the large ramp. Engage the two new vorts at the bottom of the ramp with the hornet gun.

Move next to the second sandbag wall and shoot hornets over it to hit the vorts, causing them to run around. Duck if they see you.