Part 17

Move past explosive containers and a dead bullsquid into a corridor.

Wait for three houndeyes to appear in the turning corridor and eliminate them with the shotgun or crowbar.

Proceed towards the water spill to reach section c1a4f.

In the large room with hanging cables and barnacle tongues, lob a grenade at the bullsquid chewing on a dead scientist, then fire your assault rifle at it. Alternatively, leave it undisturbed.

Locate and use the first aid station in the room's opposite corner (to the right of entry) to heal.

Get onto the narrow platform extending from the main floor.

Crouch-jump onto the platform's right-hand railing, then jump to the ladder against the wall.

At the bottom of the ladder, turn to face the short pipe underneath it.

Crouch-strafe or jump off the ladder onto the pipe. If you miss, hit the "Jump" key to let go of the ladder (quicksave first to avoid landing in toxic water).

Once on the pipe, jump onto the nearby flooring.

Use the first aid station near the scientist if needed.

Continue past a large pipe leaking toxic goo.

Take a running jump-crouch onto the pipe, walk along it to bypass the goo, and drop to the floor.

Double-barrel the zombie in the head and move past it to find a small movable platform. (Optional: Lure the zombie into the toxic goo to kill it.)

Get on the movable platform and press its button, crouching to avoid the bullsquid's spit from below.

After the spit stops, climb the adjacent ladder and drop onto the walkway on either side.

Move along the wall, staying close to avoid a fast-moving platform that can splattify you.

Reach the base of another ladder and quickly climb it after the fast platform passes.

At the top, turn around and walk or jump onto the large slanty thing. Press the red button at its top.

Jump onto the top of the reactor where a scientist is located.

Move across to another slanty thing, press the button at its top, and run down to a ladder.

Climb partway down the ladder and watch for the fast platform.

Move to the bottom of the ladder and get against a wall when it is safe.

Carefully make your way along the walkway back to the top of the ladder leading to the movable platform.

Climb down to the movable platform (or drop carefully) and use its controls to return to the area near the toxic spill.

Cross the pipe to avoid the spill and use the first aid station near the scientist if necessary.

Drop back onto the pipe segment next to the big ladder and climb to its top.

Turn on your flashlight and slowly climb back down the ladder, looking for a small ridge on the large pillar to the right.

Crouch-strafe carefully onto the ridge and crouch-walk along it to a point where you can drop to the floor without taking damage.

Push or pull one of the small metal boxes near the first aid station through the doorway and place it next to the large metal box.

Jump onto the small box, then crouch-jump onto the large box.

Jump-crouch onto the thick metal cable running along the wall and follow it until you can drop to the floor past the electrified water spill.

Move past the spill to return to section c1a4b.

In section c1a4b, move until you reach the bridge with explosives.

Recross the bridge to the door-switch room and use the switch to return to section c1a4i.

In section c1a4i, prepare to jump two large walkway gaps (quicksave before each).

Break off the boards on the boarded-over doorway with the crowbar and wait for the tentacles to calm down.

Climb back up to the top level of the firing chamber, quicksaving frequently and quickrestoring when taking damage.

Climb the first ladder on the left as you enter the firing chamber, then crouch-walk away or toss a grenade to avoid tentacle attacks.

Repeat this process for the next two ladders.

Resupply on grenades in the room past the firing chamber's upper platform.

Return to the control room, watching for a new floor gap.

This is your last chance to visit the barnacle-related secret area if you have not already.