1. Continue through the doorway. Once again, your bugbait is useless, and no explanation is given.
2. Drop below here.
3. Take the only path ahead and Alyx catches up with you.
4. Alyx leads you to this elevator, where a gunfight ensues.
5. Follow Alyx to this console, where she summons the capsule holding her father.
6. Stick with Alyx as she lowers a force field, and help her defeat the Overwatch. Don't let her die or the game ends.
7. Grab pulse-rifle secondary-fire ammo from the room on the right while Alyx unlocks the door on the left.
8. Once inside, Alyx assures her father that she is not leaving without him, but for the moment is sending his capsule to the teleportation chamber.
9. Alyx unlocks this door then sends you on your way.
10. Supplies (and head crabs) are through the door on the left. Use your gravity gun and crowbar to clear a path to the door ahead.
11. Alyx opens this gate for you.
12. Help yourself to this rare thirst quencher.
13. Unable to unlock this next gate, Alyx instructs you to backtrack to the office (inset).
14. From the video monitor, Alyx reveals that a ventilation shaft is behind these shelves. Knock them over with your gravity gun, bust open the grate with your crowbar, then proceed through the shaft.
15. Beware these nasty creepy crawlies inside. A few more steps ahead is the exit. Alyx warns of multiple Combine signals in the area.
16. Pop the grate with your gravity gun and it will trigger the claymore as it drops through the laser. Use your pistol to take out the multiple head crabs crawling the area.
17. To the right are these supply crates. The one behind glass is inaccessible for the moment.
18. To the left is this gate, which Alyx promptly opens. Enter the office straight ahead.
19. Bust open the supply crate. A trunk with grenades is to the right. Alyx calls your attention to Overwatch on the monitor.
20. The Overwatch open the gate on the right as they advance. Toss a grenade through it to topple a pair of turrets after you finish off the troops with your pulse rifle.
21. Battle another pair of Overwatch (inset), then pause to spot another troop waiting in ambush. You can see his leg in this shot. Take him out then toss a grenade through the forcefield ahead where more troops await.
22. Lob a grenade into this office to destroy the plug powering the force field.
23. Topple this turret with your gravity gun's primary fire.
24. Hurl another grenade to topple these turrets. The crate you couldn't reach a moment ago is to their right. Enter the door on your immediate left to load the next area.
25. Next, enter this control room. Drop the solitary Overwatch inside, grab rockets from the crate on the left (as well as pulse rifle secondary-fire ammo visible in front of the crate) and refill on health at the station on the right. Press the red button ahead to disable the force fields on the turrets, as Alyx has reprogrammed them to defend you.
26. Now for a fun sequence where you have to defend the control room from several waves of Overwatch. I had good success putting the turrets in these positions. They tended to be toppled quickly in a more forward position.
27. You'll know it's over when you take out this final Overwatch behind you. Here, I drop him with the crossbow.
28. After what seems like an eternity, Alyx finally drops in from the ceiling vent above.
29. Watch as Alyx hacks this terminal, revealing a shocking tale of deception!
30. Once Alyx disables the force fields, follow the corridor outside to this doorway. Use your gravity gun to clear the way.
31. Descend the stairs, meeting up with these head crabs at the bottom. Continue through the door on the left, then make a quick right to find an ammo crate. The way ahead is through another door on the left.
32. You'll then come to this room with electrified water below, which must be avoided. Ready your pistol then drop to position (1), where you'll battle a pair of head crabs. Take out the barnacle on the ceiling, his tongue visible on the right. Jump as indicated to position (2).
33. Use your gravity gun to float a pair of barrels. Reposition them one step at a time and reach the stairs ahead.
34. Keep left to find this zombie. (Cool shot, huh?) Beware the three zombies on your back. Use your SMG, as you'll be expending plenty of ammo. To the right is a health station and a crate with energy.
35. Climb the nearby stairs then use your crowbar and gravity gun to clear this doorway. Under the debris is a supply crate with more energy.
36. Up another stairway is a firefight with several Overwatch on the left. If you're full-up on pulse-rifle secondary-fire ammo, this is a good spot to use it, as there's another round in the office behind you, as well as grenades.
37. Hop over the railing, and Alyx alerts you to more incoming troops, then she suggests you look for more automated turrets. Here they are. Before disarming their force fields, retrieve ammo from the neighboring corridor, and a round of pulse-rifle secondary ammo from a nearby room.
38. This seemed to be the obvious configuration. There's less ground to hold, you can easily get to your turrets, and you can duck into the turret's storage lockers for cover. (I survived several grenade blasts that way.) There's also health and energy terminals available. Be sure to upright your turrets if they're knocked down -- just lift them high enough for the tripod legs to right themselves.
39. Overwatch will attack through the doors, as well as from the walkway above as seen here. Help out your turrets or else they'll become overwhelmed. Eventually Manhacks will join the fray, and Alyx will warn of an especially large number of Overwatch on their way.
40. After the final wave is defeated, Alyx will hop over the railing and greet you here. She assures that she won't leave you again.
41. Alyx unlocks this gate on the left. Use the health and energy stations visible on the left, then follow Alyx through the corridor to load the next area.
42. Alyx stops at this door -- you'll have to go first. Just make sure to equip your SMG first, you'll soon be firing plenty of ammo.
43. It's an Overwatch ambush! The lights are cut, then the Overwatch toss flares as they fire away at you and Alyx.
44. I tried using the gravity gun to toss debris at the troops, but I found the SMG to be a better weapon in this fight. Flush out the room on the left, then press on to the corner ahead.
45. Follow Alyx up some stairs, then use this medical station before continuing through the doorway.
46. Next up is this entertaining sequence where Alyx confronts Dr. Mossman. It's these scripted sequences that keep me going, I really enjoy them. This sequence is when I noticed that Dr. Mossman is voice-acted by Michelle Forbes (Ensign Ro - Star Trek, Admiral Cain - Battlestar Galactica).
47. Now in the teleportation facility, Alyx retrieves her father, intent on teleporting him back to Dr. Kleiner's lab. But the duplicitous Dr. Mossman has other plans.
48. Time for another turret fight. Alyx will deactivate the force fields on the lockers. Fill up on health and energy at these stations before placing the turrets. The Overwatch will charge once you've placed the second turret of three.
49. I found this placement works well. This turret battle is much easier than the previous two.
50. The progress of the battle is revealed as this green light advances toward the teleportation chamber.
51. Once the teleporter is charged, follow Alyx into the chamber.
52. A previously-unseen type of troops storm the facility once you're inside the chamber, but they are not able to abort your escape.
53. You arrive at Dr. Kleiner's lab (a week later), and this reunion ensues with Barney, Dr. Kleiner, and Dog.
54. Search the area for supplies, including a medkit (inset), the energy station ahead, and the supply crate atop the ladder.
55. Bust open these supply crates, and grab ammo from the green trunk on the left. When you're ready to leave, drop through the indicated hole in the wall to end the level.