-- walk-through --

Unknown source (it was printed for me and had no link mentioned); I scanned it, converted it to text with OCR software, copy-edited it, made some tweaks and added links to Wikipedia.
Note that some steps appear to be missing (where there’s just a question mark). I actually just respected the layout. (This document uses lists so I didn’t do any counting.)

01. Anomalous Materials

  1. Follow the green stripe to the locker room and then left to the M.E.V. room. Press the button to open the storage door for the suit and take it.
  2. Follow the blue stripe to the security door; the guard will open it.
  3. Get on the elevator and use the button to activate it.
  4. The three scientists will talk for a bit and then one of them opens the door.
  5. Take the elevator to the test lab.
  6. The two scientists talk for a bit and then they open the door.
  7. Climb to the platform, wait for the switch to open, and press the switch.
  8. Go down to the cage, which will open soon, then push the cart into the particle beam.
  9. Watch the fireworks! :)

02. Unforeseen Consequences

  1. Exit the room; use broken panel.
  2. Wander back to the security station; go through the hole in the wall.
  3. Watch out for the headcrabs and the exploding shelves!
  4. Exit through the air duct.
  5. Get the gun from the dead guard.
  6. Go to the end, drop down into the sewers
  7. Find the valve, turn it, then find an open grate (not the one you got in with)
  8. There’s a big switch above the platform, use it, then get on the lift
  9. The grated bridge will break
  10. Jump on the silver tubes to get around
  11. Jump into the water, go left and up the ladder, out the door, then in the door
  12. Jump across all the boxes.
  13. After following the corridors, you’ll end up opposite the water area. GO RIGHT and take the elevator

03. Office Complex

  1. Break the grate near the electrical wire, crawl through there
  2. Go to the electrical room, turn off the power
  3. Go out, now that electrical wire is off
  4. Break the glass, climb through
  5. Break through the crates
  6. Get the shotgun
  7. Shoot the alien attacking the guard, if the guard lives he will open the door which has more ammo and health inside
  8. Go back to the flooded room, climb in there, break the grate on the air duct and go in there
  9. Duck under the fan
  10. Push the crates around so you can get to the ladder
  11. Break all the grates. Watch out for the sentry gun; you can either shoot it or jump down and run for the power switch under it.
  12. Up the stairs, you can have the guard follow you by “using” him
  13. Go out the door marked “exit”
  14. Up the stairs
  15. Another guard to help you
  16. Go down left to get some grenades
  17. Go right, then break open the boarded up doorway with the crowbar
  18. Open the freezer door with the handle on the left
  19. Go left and find the red switch that activates the cart on the ceiling
  20. Climb up the ladder go through all the air vents to get on the moving cart
  21. Go across to the other air vent
  22. Climb up on the air ducts to the exit at the left
  23. Another guard to help
  24. Go up the stairs
  25. Jump into the elevator shaft onto the ladder, climb up to the top
  26. Get on top of the elevator and break in, then go out the elevator doors

04. We’ve got Hostiles

  1. To destroy the sentry gun make a run for the pillar, then strafe out and shoot it
  2. The trip bombs can be jumped over and ducked under
  3. To take out the sentry guns, use one of the grenades on EACH of the guns. They will not fire at you unless you cross the red laser beam.
  4. There is another pair of sentry guns near the back - break the crates to see one, climb over them to get to the other one
  5. You can just trip the sentry lasers - they activate the guns you just destroyed
  6. Use a grenade or two to take out the pair of sentry guns; after you take out the guns you can trip the beams in safety
  7. To open the fire door, use the switch on the left
  8. You can trip the red beams, but not the blue ones; make sure to not move the boxes the blue trip bombs look at
  9. Climb up the ladders to exit; while the Marine shoots the scientist, throw a grenade at him - you’ll need to hold the grenade for a second or the Marine will run away before it explodes
  10. Exit by the freight elevator
  11. Exit by going out the fire door on the catwalk
  12. When you come to the T, go right
  13. Walk up the conveyor belt, climb the boxes, and then get on the conveyor belt
  14. Destroy the sentry guns below you with a grenade, then jump down; watch out for the sentry gun behind the open fire door!
  15. Go up the stairs in the warehouse; if you’re patient, you can get the Marines to be eaten by the vine monsters
  16. Climb up the catwalks to the top and then go down the corridor
  17. Kill all the Marines first and then go down to the warehouse floor
  18. Take the freight elevator up
  19. You do not have to kill the Marines the Osprey drops off; just stick to the outside and make a run for the bunker. Go down the ladder in there.
  20. Open the door to the ventilation shaft; go down to the bottom
  21. You can drop past the fan blades by going to the far right corner and dropping down
  22. Go out the middle vent
  23. Use the control on the computer to open the silo door; exit

05. Blast Pit

  1. Break the barrier, duck under the hazard barriers
  2. Go up to the control room on the right, use the switch, exit on the freight elevator
  3. Jump on the cart, run it at full speed until you get to the end. Stop the car just after breaking through the guard rail.
  4. Jump up onto the walkway, go around the slime via the walkway to get to the ladder into the pipe.
  5. Go in the pipe
  6. Climb the ladder to get on top of the pipe so you can get past the slime
  7. You should now be in a big slime-filled room.
  8. Walk along he pipes to get to the elevator up
  9. At the top there is a spitter, shoot the canisters next to it to kill it
  10. If the spitter blew up the bridge, jump across
  11. Use the switch to open the airlock
  12. You cannot save the scientist
  13. Before going into the silo with the monster, stand next to the doorway and shoot the crates blocking the ladder on the left. If you wait till you’re there, the monster will hear you breaking them and attack.
  14. Go into the room with the monster, if you walk then it can’t hear or attack you. Go to the second level from the bottom.
  15. Go across the bridge and follow the red and blue pipes
  16. Go into the sewer grate by ducking on top of it and using the crowbar
  17. Go left at the T to get to the ladder going up
  18. You’re now in the room with the big fan at the bottom. Go down the ladders and get to the switch...
  19. As soon as you flip the switch under the blades, hurry up the first ladder and wait.
  20. After 3-4 seconds, throw a grenade up, over the fan. The grenade will fly to the top, breaking the wood. (Alternatively just jump up there and play with a crowbar but the grenade is cool.)
  21. If you haven’t already done so, jump on the fan - really!
  22. At the top, break the grate to exit
  23. After going through the vents you enter the oxy/fuel control room. Turn on both switches at the control panel. Both lights must be one.
  24. You can now exit by the ladder.
  25. ?
  26. Go to the lower level of the silo with the monster in it.
  27. Jump across the broken walkway
  28. After crossing the puddle of water, go to the room with the crates in it. Push those crates over the water making a sort of bridge over it. Make sure you can jump onto the crates WITHOUT touching the water at all.
  29. Go to the catwalk and press the elevator call button. Get on the elevator and start it moving.
  30. The elevator will stop part way down. Jump to the ladder on the wall on the left. If you’re too slow the elevator will fall.
  31. At the bottom, you can jump on the pipes to avoid the radiation on the floor.
  32. Take the stairs to get up to the power generator controls. There is a switch on each side of the centre structure that need to be turned on. Make sure you’re not on top when both are activated!
  33. The power is now on; exit the way you entered
  34. When climbing up the elevator shaft, there is a ledge near the top (not the platform at the top) that you can get on and walk around so you won’t get hurt jumping off
  35. Use the crates you moved over the water to get safely past; if you didn’t push the crates there don’t bother now, you’re going to get electrocuted no matter what
  36. Make your way back to the top of the monster’s silo, to the control room; press ‘fire’ and enjoy the show!
  37. If not all three lights are on in the control room, you did something wrong - go back to step 1
  38. Exit out the hole that the monster left in the floor
  39. You can get the .357 in the room with the water in it
  40. Exit out the holes in the bottom of the pool; you will need to go back up on the side with ONE pipe, not the one with two
  41. Stay on the pipes and walk to the end, where there is a wheel. Jump off that pipe and into the one on the wall with the broken grate in it.
  42. Walk carefully! The pipe will break at the purple part. If you jump back you can avoid going down with it.
  43. Go left, squeeze down between the pipe and the girder, down to the ceiling. Or, just take the health loss - there are two medpacks at the bottom.

06. Power Up

(Maps : c2a1.bsp, c2a1a.bsp, c2a1b.bsp)

  1. Run straight across, while the monster is distracted with the Marines
  2. At the Y go left
  3. Go down the tunnels
  4. Use the wheel to open the red doors, climb up the shaft to the top
  5. Cross the open area and go up the other side.
  6. Go left, towards the power generator
  7. Press the button to send the elevator down. DON’T GET ON. Wait till it gets to the bottom, then shoot the trip mines; THEN go down.
  8. Exit by the stairs down. Go all the way to the bottom and break the crates blocking the generator from working.
  9. Go up a level and turn on the left side fan.
  10. Go back up the stairs to the elevator, take the elevator up
  11. Go out the way you came in, all the way to where the map of the base is.
  12. Go down the shaft, back down the corridors, all the way to the boarded up doorway to "Track Control"
  13. Do not pull the switch in track control
  14. Jump out the window and go down the big tunnel on the left. The monster will follow you but will not attack. At the end of the tunnel, get on the catwalk and throw the switch at the end, the monster will be electrocuted and blow up.
  15. Exit by the doorway, which leads back around.
  16. Get on the car and drive it all the way forward (onto the lazy susan). The car will stop on its own so just floor it.
  17. Go back to track control and pull the switch. Jump back out and onto the car and start it up.
  18. The car will stop at the guard, use the switch on the left to open the gate.
  19. The water will electrocute you.
  20. Keep the train going straight until the second track switch. Shoot it to change the tracks to going straight.
  21. Stop at the platform with the stairs and the spitter
  22. Take out the sentry gun and use the switch to move the crane
  23. Shoot the next track switch to go through where the crane was.
  24. Open the guard rail and continue
  25. The car will stop at the end of the line, I suggest taking out the Marines on the left one by one, as they don’t notice when you shoot their team mate.
  26. ?
  27. To get past the mounted gun, run up right next to it (on the side) and toss a grenade in. The sandbags will protect you from the blast.
  28. Go through the blast doors; shoot or grenade the trip bombs.
  29. You are now in the missile silo. Go down a level to get to another car.
  30. If you duck under the laser beams, the guns will ignore you.
  31. To take out the rocket launcher, simply set the car to full speed and get off; it will stop soon, so don’t worry about keeping up with it.
  32. After killing the lightning monsters, jump on the green boxes by doing a ‘long jump’ (see the Hazard Course)
  33. Use the switch in the control room to open the gate blocking the car.
  34. Go to the next gate, then kill everything in the room; to destroy the mounted gun, toss a grenade into the bunker.
  35. The switch for the gate is near the bunker.
  36. To destroy the trip mines, again let the car go on its own; it will stop soon.
  37. Open the gate and continue.
  38. To get past the rocket turret simply duck behind your speeding car until you reach the guard - kill him, then proceed
  39. Shoot the track switch so you can go straight.
  40. Take the ladder down; make sure not to trip the red laser beam!
  41. You can take out all the sentry guns with grenades from the control room.
  42. To take out the mounted gun, first kill the Marine on the platform on the right, then jump over the tracks and hide behind the crates. Push (or break) those to get up to the sand-backed wall, go around the right of that. You can then kill the Marine if you want to with a grenade.
  43. Go through the blast doors.
  44. To get past the lasers, push the big box under the last beam. You can then walk onto that from the stairs (duck under the first two); then jump over the last, from the box. (Or push the small box next to the big one... )
  45. Go up to the control room and press the ‘Launch’ button.
  46. Exit out the blast doors
  47. Exit on the now-opened big doors to the left of the blast doors

07. Apprehension

(Maps : c2a3.bsp, c2a3a.bsp, c2a3b.bsp, c2a3c.bsp, c2a3d.bsp, c2a3e.bsp)

  1. Get off the train, it can’t be stopped
  2. To release the canisters to make a floating bridge, swim down and ‘use’ the lock.
  3. Go around the catwalks, jump into the water.
  4. Swim around for a while until you find the exit, which is a sloping ramp.
  5. In the room with the big fish in it, go around the catwalks to get to the top so that you can get in the cage which has the crossbow in it.
  6. After the cage drops, swim over to the big pipe and get on top of it. You can stand there and shoot the monster with the crossbow or with the 9mm (or stay in the cage and kill the monster from there)
  7. After killing the monster, swim down, open the grate and then go through it.
  8. Go up the stairs.
  9. Go around on the catwalks (don’t fall off).
  10. Jump around the electrical wire on the left - I had to take a health hit. You can also jump into the water and swim around.
  11. Press the button on the control panel, which starts the pistons. Jump on the pistons to get across the room.
  12. Kill the stuff in the room and then the scientist will open the door.
  13. Nothing special in the cold room; go right, left, and right to get to the ladder.
  14. I ended up having to use detpacks in the doorways to kill the THREE invisible guys.
  15. After killing them, go up the ramp to get to the surface access control. Hold down ‘use’ to open the doors.
  16. Exit through surface doors. [[cut-scene]]
  17. In the trash compactor, calmly climb the crates to the top before you are horribly squished.
  18. DO NOT forget the crowbar!
  19. Exit by the grate at the bottom of one of the backs of pit.

08. Residue Processing

(Maps : c2a4.bsp, c2a4a.bsp, c2a4b.bsp, c2a4c.bsp, c2a4d.bsp, c2a4e.bsp, c2a4f.bsp, c2a4g.bsp)

  1. Use the flow control knob, then go down the tower
  2. Jump in the vat (sort of) so you can exit by the pipe at the other side
  3. Walk on the pipes to get to the next vat
  4. Either jump on the stirrers or walk around the outside of the vat to get to the other side.
  5. Walk for a while, you can duck under the big spinning wheel
  6. When you get to the conveyor belts go right, to the switches
  7. Flip the centre switch (so they’re all up)
  8. Go back to the control room, press the green button - this will stop the smashers
  9. Go onto whatever conveyor belt is open, ride it through, jump as necessary
  10. To get past the next sets of smashers, just time it all right
  11. This part is tough, keep dropping to the next crossing conveyor belt until you get to the one with two under it. Ride the first one, the one leaving the room. There are two trip mines so use a grenade or gun to destroy them.
  12. Take either passage (they lead to the same place).

09. Questionable Ethics

  1. Shoot the houndeyes BEFORE going into the room. One shot from the .357 will kill them.
  2. To open the electrified door, shoot the thing on the fence that the lightning is coming out of. (Or use the crowbar... Just avoid electrocution... )
  3. The big ol’ monster behind the glass WILL ESCAPE if you shoot the control switch. (Note : you must break the switch to exit.) If you run away, the monster will not follow.
  4. You can zap the pen full of headcrabs by using the switch, but it’s not needed, and a Marine will come if you do.
  5. Another guard to help you out
  6. In the two cells filled with headcrabs there is a monster gun and the crossbow. It’s worth it to get them both. Simply open the doors, then go into the control room and activate the machine, it will kill everything in the room.
  7. At the T, go right
  8. Do not trip the mines in the next room, go around up to the control room, then shoot the one on the left.
  9. As soon as you shoot it, drop back out of sight. If the monster doesn’t see you then the Marines will shoot it, making your job much easier.
  10. After everything is dead, exit by the door that used to be protected by the trip mines.
  11. Find the stairs and go up them
  12. Again, if you let the Marines fight the monsters, many will die, letting you save ammo :)
  13. Turn on all four lasers, then go back to the room that says "do not obstruct laser shield"
  14. Do the opposite of what the sign says - move the crate on the left so that it blocks the shield.
  15. Use the control panel, it will activate the laser which will blow a hole in the wall, exit through there.
  16. Jump on the pipes to avoid damage when going down.
  17. BEFORE having the scientists follow you, go through the gauntlet and shut the machine down, then have the scientists follow you.
  18. Go out the other door, then go left, then right, then straight.
  19. Have the scientist open the door leading to the outside
  20. Watch out for the sentry guns on the roof

10. Surface Tension

  1. You are now at the dam.
  2. Take out the turret from a long way away, two crossbow bolts will do it, just aim at the gun and fire
  3. Next run and jump into the water. There is a monster in there so either kill it or swim really fast
  4. Climb the tower and go inside it, throw the switch.
  5. Swim down to the base of the dam and turn the wheel which opens the grates, then swim out one of them
  6. You’re now at the base on the other side of the dam.
  7. Swim over to the ladder and exit through the pipes
  8. Exiting the pipe, go straight
  9. Climb the ladders to get up the wall
  10. Go towards the fence and exit through the crack right there (the other crack leads to a tentacle monster)
  11. You should now be in the minefield. Go to turn the wheel for the storm drain
  12. Exit by the sign that says "storm drain hatch"
  13. Jump into the now-open storm drain by climbing on the ledge and jumping in.
  14. The pipe exits onto a cliff, I used a M203 to take out the sentry gun.
  15. Jump down on the left, you can get across the breaking bridge by walking on the wires
  16. Go into the cavern to get the missile launcher (when the red dot is on the missile will go wherever you aim, without the dot it will fly straight)
  17. Two missiles will bring down the chopper...
  18. Exit on the right
  19. At the T go left, go slo-o-o-o-owly up the ladder and shoot the Marine with the .357 (before anyone else sees you), you will then be in a fire fight, fall back into the pipe to try and take them out one at a time. The crossbow is a good sniper weapon.
  20. It takes four missiles to take out the tank, but if you’re quick you can run into the guard house and open the gate without having to kill the tank.
  21. You can avoid the next tank by simply strafing.
  22. When the sign says “mines” there really are mines! However in this case you need to go across, (stick to the left) so that you can take out the sentry along the way (otherwise he will shoot you when you get over there)
  23. After crossing the two trip mines, watch out on the right for the sniper. Either use a rocket or whatever to shoot the grey thing right next to the gun barrel
  24. Now you have to cross a minefield. Just stay next to the building on the left.
  25. Shoot the explosive barrels to cut the power
  26. Climb the broken tower to get to the roof
  27. Take the first left to get to the break in the roof, drop in.
  28. Jump on the railing to get past the beam on the stairs
  29. Jump over the third and duck under the fourth to get to the warehouse floor
  30. Go left, break the boxes on the left but not the ones right next to it.
  31. Break through the partially broken crate, making sure not to break the sides, leaving you a doorway
  32. After going through the new doorway, go right and break the crate on the lift. Then go out and right to get up to the control room
  33. Jump on the lift, which now allows you to jump over the lasers onto the elevator, which you can now exit on.
  34. The aliens will get dropped off in a ship, then the area will be carpet bombed, killing the monsters.
  35. Simply run past the tank, strafing to dodge.
  36. Go right, there is a sentry in the lower right corner of the sniper spot
  37. Go up the stairs in the first warehouse, get the guard to open the storage room.
  38. After loading up, bring the guard with you
  39. Jump out the window, then go along the ledge to get to the ladder going to the roof of the other building
  40. You don’t have to kill everyone in the bombed-out building, but it makes it easier. You need to jump across to the exit on the other side of the building
  41. Go across and down under the howitzer to get the guard, bring him back to open the door under the gun.
  42. Use the big gun to blow open the big doors, then exit by those.
  43. This next part is tricky, you need to kill the three monsters, then make a run for the jump pad before more spawn in. You can try killing them all, but there are about 20 total
  44. For the next part, let them fight it out, then play clean-up
  45. Exit by the vent
  46. After killing the Marines, exit by the door on the right. A grenade will be thrown in; you MUST get past it and out into the open before it goes off. It will seal the door. (Or use the elevator jack : bring it down, turn it back on and quickly get on it, and then jump onto the ledge.)
  47. Use the big gun to get out
  48. You need to jump over the broken catwalk, I suggest jumping on the railing to get past the first break.
  49. ?
  50. ?
  51. Open the pipe and climb through it
  52. At the end, where the stairs are, get the guard to follow you, he will open the door at the bottom
  53. Again have the guard follow you, he will open the next door too.
  54. You’ll now meet another fire monster - run like hell to the right and you won’t have to face him.
  55. Jump over the wall, then jump on top of the silo to use the targeting computer. Play with the targeting computer to get the crosshairs to target 1) the walls on the left compound, 2) the big door over in the corner, and 3) knock down the tower
  56. Once those are destroyed, use the fallen tower and exit by the tunnel

11. Forget about Freeman

  1. Step right, wait for the third segment to fall, then jump on it to get to the exit on the left.
  2. At the T go right
  3. Use the wheel to open the hatch, go down
  4. If you trip the laser, the gun will shoot you.
  5. Jump over the grate on a west tunnel to exit
  6. Go through the tunnels, at the tank either destroy it or simply run past
  7. Take the elevator down
  8. At the T go right, use the tank to blow open the door. (I had to use a bunch of trip mines to kill them all)
  9. To kill the lightning gun, hide on the right, then pop up/down to shoot at it before it has a chance to fire back. To kill the bee-gunners use your own bee gun and fire from a covered position.

12. Lambda Core

  1. Use the control room to start the elevator down.
  2. More of those invisible people...
  3. Get up top and find the elevator down to exit
  4. Kill everything, then the scientist will open the door.
  5. Go right to get to the ghostbuster gun, then back to the coolant system elevator.
  6. Go and flood coolant system 1 by turning on its generator.
  7. To get to #2, simply go through the rubble
  8. Go back to the aux. reactor. Jump down and go through the maintenance access pipe.
  9. Open both valves to flood the room; to avoid the sparks simply time your moves.
  10. Climb up the elevator shaft, jump off the ladder to get to the upper level.
  11. Use the steam to kill the bad guys (or just shoot them), you can play with a teleporter here too
  12. Go through the door marked "Core Level B"
  13. Teleporter entrances are orange, teleporter exits are green. You need to time when you jump in order to make it to the top.
  14. At the top, exit by the door. The teleporter takes you to the bottom.
  15. Take the ladder up, the scientist will open the door.
  16. The scientist will open the door, MAKE SURE to get the jump-pack!
  17. This is a really tricky part, you need to keep the scientist (and yourself) alive until the scientist gives the okay to jump into the teleporter.

13. Xen

  1. Use the long jump to jump all around, you need to get to the lower level with all the lights.
  2. Find the health pool, there is an entrance near there to the interior of the place
  3. Use all the control things, then break all the lattice stuff which releases the yellow crystals, which activate the transporter.

14. Gonarch’s Lair

  1. Shoot the spider in the sack, anywhere else won’t work. Hint : there is a health pool on the outside
  2. Enough hits will make it run off...
  3. Follow it!
  4. Play with it again; this time the health pool is under the floor, which can be accessed from the break in the wall on the left or by dropping down the centre.
  5. Again, follow it!
  6. Shooting it from the top of the cliff does nothing. To avoid damage while getting down, there are ledges...if you look hard.
  7. Drop below it; if you hide behind the tree things on the left, they will kill most of the little guys for you.
  8. That’s it, kill it and get on with it! :)

15. Interloper

  1. Find the healing cave on the left (I think). Don’t fall into any pits!
  2. In the healing cave is a small yellow cave; go down there!
  3. Go through all that; at the end is a white column held up with the lattice stuff - break that then ride the tower up.
  4. Ride all the steps down, then jump on one of the beasts’ backs and ride it to the teleporter.
  5. To get to the teleporter, you will have to go above the three-headed monster (walk, again).
  6. DO NOT SHOOT THE MONSTERS (yet)! If you leave them alone, they will leave you alone.
  7. Take the lifts up to the top and get on the conveyor without a blue force field on it
  8. Stay on the upper level and go around till you can go up again.
  9. Once up, go right.
  10. Tip : don’t shoot the cocoons, they have things in them... very bad things...
  11. I heard you can just jump over the next cocoons, but I was unable to do it. I took a detpack, threw it under them, switched to the shotgun, shot the cocoon, switched back to the detpack, and blew it; then killed the second monster with more conventional means.
  12. Exit by the air duct with the floating globs of light.
  13. You are now in a big tall room, ride the lifts up to the teleporter at the top. Note : taking the side room (from the second-to-top level) is not needed, but there are grenades and such there.
  14. Jump over to the teleporter with the kick-ass lightning on it.

16. Nihilanth

  1. Shoot the triangles!
  2. Shoot it until its head pops (the head just opens up on the top - you may miss this lovely event if you’re not bouncing up high).
  3. Nuke its brain stem (one or two detpacks dropped in his gaping cranium should do the trick).
  4. Bang - it’s all over!

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