Part 34

Sneak-shoot surviving marines, preferably with the pistol to conserve .357 ammo.

Ensure all enemies are eliminated, then collect any armor batteries and weapons from the fallen marines.

Return to your security guard and escort him back to the computer room.

Proceed through the winding hallway. If the security guard cannot reach the hallway, you may need to eliminate him for his pistol.

Sneak-shoot the marine at the left end of the hallway with the .357.

Move down the hallway to a door on the left. A shortcut is possible by using the "Use item" key against the door's left side to activate the panel on the other side, but this skips the gauss gun.

To proceed the recommended way, go through the door and shut off the "surgical unit" using the control panel to the left of the walkway.

Retrieve a scientist from the back room and escort him back to the lobby, talking to him as needed to ensure he follows.

Go down the hall to the room with several crates. Break all crates with the crowbar except the one with a tripmine aimed at it. Collect bullet clips and use the first aid station.

Return to the hallway path split and go the other way to find headcrab cages.

Lure the headcrabs out by running in front of their cages, then move to a safe location and use your pistol to shoot them.

After all headcrabs are eliminated, proceed through the doors back to the lobby.

Check the lobby's side hallway for a marine and eliminate him with the pistol if present.

Use the lobby's HEV station if you need armor.

Return to the headcrab cage area and go up the stairs between the cages to reach section c2a4f.

In section c2a4f, near the top of the second set of stairs, wait for the sounds of marines fighting bullsquids to cease.

Use the crossbow in zoom mode to peek around the corner. If a bullsquid is near a large crate, shoot the crate with the pistol to allow the bullsquid to reach its target.

Shoot any visible marines in the head with the crossbow.

Move forward to an open doorway on your right. Be prepared to sneak-shoot any bullsquid in the room beyond with the pistol.

Continue down the main hall, watching for marines at the other end.

To use a bullsquid distraction: Peek around the corner at the top of the stairs to attract a marine, then retreat down a few steps and equip the shotgun. The marine may engage a bullsquid in a side room, allowing you to charge or wait for them to come within shotgun range.

Near the end of the main hall, check the room on the right for marines and break the boxes outside for ammo.

In the marines' room, collect ammo boxes from shelves and use the first aid station if needed. Press the big red button on a panel to start a laser.

Go down a short side corridor to a room with houndeyes. Quickly kill them with the assault rifle or shotgun, then press the room's big red button to activate its laser.

Return to the main hallway and find another branch to the right with explosive crates. Move into this hall just far enough to hear voices, then wait for the guard with the experimental weapon to overcharge it.

Go down the side hall and into the room beyond to pick up the experimental gauss gun (tau cannon).

Find and use this room's laser-starting button.

Return to the main hallway and go back to the room where you previously dealt with a bullsquid. Collect armor batteries from the shelves if needed, then hit that room's laser-starting button.

Go back down the main hall to the primary laser room.

Push the movable crate to obstruct the laser shield when it lowers.

Press the big yellow button on the nearby console to fire the laser, creating a hole in the wall.

After the laser stops firing, crouch-walk slowly through the hole to drop onto a small metal ridge against the wall.

Walk along the ridge to the corner and drop onto a square joint on a vertical pipe.

From there, drop to the next small metal ridge against the wall, then to a curved section of pipe below it to reach section c2a4e.