1. Don't get any closer to these supplies than I am here, or else you'll crash through the ceiling to an amused Alyx. Instead, grab them with your Gravity Gun then return down the ladder.

2. Keep right at the junction again and follow the shaft until it collapses in front of this mine. Don't disturb the mine; instead, pop open the grate above and step up.

3. Find the entire room booby-trapped. Escape to the elevator straight-ahead by hopping along the barrels and bench.

4. The lift drops into the water below. Use your Gravity Gun to punch open the ceiling grate, then swim to the surface. Beware the barnacle tongues dangling above.

5. The neighboring room is likewise booby-trapped. Shoot one of the barrels to set it ablaze, then quickly dive into the water to survive the resulting explosions.

6. Find supplies and a toxic head crab inside.

7. Use your Gravity Gun to uncover this vent then climb in with the aid of the neighboring barrel.

8. The vent leads to this ledge which you can follow to reach the ladder ahead.

9. Jump to the ledge in front of this grate seen below, then pop it open with your Gravity Gun and enter the vent. Be careful to avoid the barnacles.

10. Follow the vent to this opening. The falling grate triggers another set of explosions, so be sure to wait before jumping in.

11. Deactivate any remaining mines then use the panel ahead to turn on the power and unlock the door for Alyx.

12. Exit through this door, opposite.

13. Follow the hallway to this next booby-trapped room, complete with crawling zombie. Best to just shoot the flaming barrels from the hallway so it's relatively safe before you even enter. Be sure to deactivate the mine in the far left corner.

14. Note this force field on the left. Beware the stairs on the right -- Combine are about to blast through the door.

15. Fight your way up the stairs to this room. Grab the crossbow on the shelf behind this soldier before pulling the green plug seen upper-left to deactivate the force field at the bottom of the stairs.

16. Once outside, your new crossbow does a great job sniping the rappelling troops. Hold the left trigger to activate your crossbow scope. Supplies can be lifted over the fence on the right.

17. After a brief street fight, the underground lead you through this door to a safe house.

18. Plenty of supplies are found along the way. Be sure to find this medkit after listening to Dr. Kleiner on the nearby TV.

19. Ascend the stairs then pull the planks off this door to bypass the stairs blocked by a head crab bomb. Zombines are on the other side.

20. Enter this room on the right, careful to avoid the rotted floor boards. Otherwise you'll fall into a zombie pit below.

21. Meet up with Barney on the top floor of the safe house. He'll lower this bridge for you and Alyx, leading to a diversionary second route to the evacuation trains. He'll also hand you an item you have probably been missing - a crowbar.

22. Cross the bridge then enter the building through this window on the right. Break through a plank to another short bridge beyond.

23. Ascend a flight of toxic-head-crab-infested stairs to yet another bridge. Pull the plank away from the crank to lower the bridge.

24. Cross the bridge to this hospital. Find more crossbow ammo next to a washer/dryer then battle these zombies. Toss the bench with your Gravity Gun to trip the mines ahead for safe passage.

25. Ascend another flight of stairs to this attic. Retrieve the grenade launder once the comrade is killed then take up position at this crate for infinite ammunition.

26. Your task is to bring down this gunship. As before, try swirling your site to help the rockets dodge the gunship's fire.

27. Once the airship crashes into the attic, drop to the floor below and collect any remaining supplies. The way out is through this door, after these troops blast through.

28. Toss the box through the lasers to trigger the mines. Alyx will then lower the force field. Beware of the mine on the other side.

29. Time for an extended run-and-gun, complete with soundtrack. A supply crate and a zombie are in the first room to the left. The second room on the left is empty.

30. Someone's throwing a major party around the next bend and they forgot to invite you. Your pulse rifle does a good job correcting their manners.

31. These fools ask Alyx to dance once you reach the end of the corridor. Her shotgun tells them she's a one-man kinda gal. Grab a supply crate from the room on the left before continuing through the door on the right.

32. Overwatch, zombines, zombies and Combine troops are getting it on in the next corridor. Try to stay out of their way until the diehards are all that's left. Collect supplies once the corridor is quiet -- just be prepared for toxic head crabs to drop through the ceiling when you enter the room on the far right.

33. A trio of zombies are chilling in the lounge, up the next corridor.

34. Gate crashers are across from the lounge -- tell them the keg is kicked.

35. Uh-oh, someone called the cops. Take out the Overwatch in the last room on the right then grab any chips and dip left lying around. The party's over.

36. The path forward is through this hole in the operating room floor.

37. Crash through the lower floor all the way to this flooded basement. Swim to the surface and battle toxic head crabs. A supply crate is in the room to the left. The way out is through the blue door ahead/right, but it's locked - for now.

38. Kill all the barnacles in the room, and position the blue barrel so that it supports the unstable bridge segment seen on the left. Activate this panel to unlock the blue door across the room far/left.

39. The water is now electrified and should be avoided. Sprint across the bridge then jump to the platform in front of the sparking panel.

40. Turn right. Jump to the pillar ahead, then follow the railing right. You can then jump to the platform adjacent to the room where you found the crate.

41. Climb through the window to the platform and exit through the now-unlocked door.

42. Ascend the stairs to this room where you'll be joined by Alyx. Open the supply crates and avoid the barnacles. Continue through the door ahead.

43. More supplies are found, guarded by toxic head crabs below. Use your gravity gun to snatch the crate and medkit seen here before dropping down.

44. This toxic zombie is the source of the head crabs. Take him out quickly -- he's called in lots of backup.

45. If you're really quick, you can mine the doors with these mines before more zombies arrive.

46. Once your preferred weapon (mine is the shotgun) quells the mayhem, grab supplies then exit through here. Turn left then keep right.

47. Find more supplies in this operating room then continue through the door on the right, just off-camera.

48. This next corridor is mined, and automatic turrets attack from the far end. Advance by rushing to the side pillars, careful to deactivate the mines as you go.

49. Be cautious of that room marked "R 344." You'll find supplies there, but zombies like to wait in ambush.

50. Once you, Alyx and the turrets have decimated the zombie assault, use your Gravity Gun to simultaneously pull the plug on the force field and on the turrets.

51. Advance down the hallway to this door and the next checkpoint.