Part 24

After shooting a marine, turn right at the ladder top to avoid being seen by those in a nearby lift. Use the first aid station if needed, grab bullets and AR grenades, then climb the next ladder.

Past the ladder top, push a wooden crate left to crouch-walk past it on the right.

Carefully sneak-shoot a marine on a board across the tracks to the right with the .357 Magnum.

Break open the wooden crate to find .357 ammo. Crouch-walk down the ledge to the right of the tracks until you pass a dead marine and see a sandbag wall ahead.

Shoot the marine behind the sandbag wall with the .357 Magnum as soon as possible; he will see you and may throw hand grenades. If he doesn't appear, try jumping across the track and moving around.

Move back along your ledge to see down the side track. If vortigaunts are near the lowered barrier arm, shoot them with the pistol to potentially draw them towards the marines.

Move forward along your ledge to a spot where you can see marines in an area between the tracks to the left. Crouch-walk back and forth between this spot and where you shot at a vortigaunt until fighting between marines and vortigaunts ceases.

Crouch-walk to the big gun behind a sandbag wall and use it to eliminate visible marines or vortigaunts ahead. (Warning: Marines may see you before you reach the gun; consider sneak-shooting them with the pistol or .357 Magnum instead.)

Jump over the track to the marines' area. Crouch-walk forward slowly to check for remaining vortigaunts across the next track and shoot them with the assault rifle or .357 Magnum if present.

Break open boxes in the marines' area for supplies. Jump across the track to where the vortigaunts were, go up the stairs, and shoot two headcrabs and any hiding vortigaunts.

Crouch-walk along the walkway to the HEV station, being careful not to be seen by the marines on the lift below.

Return to the bottom of the stairs and jump back across the tracks to the big gun emplacement. Find the stairs past the big gun, hop onto the side railing, and slowly move up it.

When you can clearly see the head of the marine past the stairs, use the .357 Magnum for a headshot (a shot that lands on the enemy's head, usually an instant kill) to kill him instantly.

Jump up to get the attention of another nearby marine, then quickly drop to the bottom of the stairs and wait for him to appear at the top to .357 him.

Past the top of the stairs, raid the radio area for health and ammo. Go to the start of the nearby corridor, avoiding the left-side room with a hidden marine.

Wait for the fight between vortigaunts and marines ahead to finish. Move to a position where you can shoot vortigaunts one at a time to lure them for easier killing.

Once all possible vortigaunts are dealt with, move into the corridor to load section c2a2c.

In section c2a2c, quickly finish off any remaining vortigaunts. Go into the large side room and break the two boxes on the floor to find .357 ammo.

Go along the walkway past the side room to some stairs. Crouch at the top of the stairs and carefully crouch-walk to sneak-shoot the marine at the bottom with the .357 Magnum, or toss a C4 satchel bomb down to blow him up. (Warning: He may not be present if the nearby conflict has already triggered; watch for other marines near the bottom of the stairs.)

Crouch-walk into the dark space under the bottom half of the stairs and break the crate to reveal an armor battery and a floor grating. Bash the grating and drop through the hole.

Move along until you find a dead marine. Use your flashlight to look past him and quickly shoot the headcrab that appears. Look around for supplies, including two more C4 satchel bombs.

Climb out of the secret area. Crouch-walk slowly down the corridor to the right of the stairs to see who survived the fight above. Quickly shoot them down.

Collect ammo from dead marines. Jump across the tracks to find a large alcove with two crates for more supplies. (Warning: If surviving marines are above the secret supply area, they may shoot you through gratings; consider eliminating them first.)

If your armor is less than 100, return to the HEV station in the previous section to charge up before continuing.

Crouch-walk carefully along the ledge on the left side of the track leading away from this area until section c2a2d loads.

In section c2a2d, crouch-walk forward to a stick-out pillar, beyond which is a raised ledge with a red railing.

Carefully sneak-shoot the three marines on that ledge with the .357 Magnum. Quicksave before starting. Crouch-walk very carefully to get into a position where you can see part of the next marine without him seeing you.

After all three marines are down, move forward.