Part 43

From the walkway, jump onto the railing and then over the large 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. Switch to the crossbow or gauss gun to finish him if he appears.

Stand in the doorway to the right of the wall hole and look left at the large floor hole. Shoot hornets into the hole until enemies below stop reacting.

Go to the big wall hole past the floor hole and look down. Fire hornets at the alien grunt fighting a marine. Quickly eliminate the grunt, then use altfire hornets to kill a marine on a distant rooftop.

Look up and fire hornets at the ceiling above to potentially hit an alien grunt.

Go to the edge of the big floor hole and destroy the largest 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 the shotgun ready to kill a hidden vortigaunt.

Go up the ramp, turn around, and shoot the high-up alien grunt you previously targeted through the ceiling. Move past the ramp's top and jump if needed to get its attention.

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

Return to the whoosh-thing and use it to reach 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. Quicksave, then equip the crossbow 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 quick kill. If you miss, quickrestore. (You may need two darts.)

Immediately after the marine is dead, move backward and crouch at the bottom of the water as a bomb 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.

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

Slowly enter their room with the hornet gun, sneak-shooting survivors with hornets. Switch to the assault rifle if needed to finish off any remaining marines.

Use the ladder to descend to their floor and check the alcove near the first aid station for hidden enemies.

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

Crouch-walk through the open hatch door, climb a short ladder, and proceed along the large pipe to its other end.

As you near the end, equip the .357 and carefully move to shoot the marine near the bottom of the stairs to the right. Finish him quickly if he spots you, before he can reach and kill the security guard.

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

Go to the top of the stairs to find the security guard. Have him follow you to the locked door and unlock it.

Leave the guard and proceed down the winding hallway past the door. You will emerge behind the short sandbag walls near the large ramp.

Engage the two new vorts near 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.