1. Emerge in a clearing and witness the Combine heading to White Forest.
2. Continue past some barrels on the left to an antlion attack in the valley. Grab supplies, all while rushing to the final thumper seen ahead.
3. Leave your gnome at the thumper then approach one of two rail tunnels. Two antlion guardians attack.
4. This is a tough fight. Try to stay within the moderate safety of the barricaded thumper seen ahead. Plenty of flammable barrels are here but I found it terribly dangerous to carry them around with two head-butting guardians about.
5. Shotgun alt-fire worked better for me. Fire quickly and accurately and both guardians will fall.
6. The Vort will lift the gate blocking this malfunctioning lift. To get it working, climb this ladder.
7. Follow this grassy path, careful to avoid the toxic headcrabs nearby.
8. Gain access to the lift by removing the plank blocking the ceiling trap.
9. Dislodge this axe and free the mechanism.
10. Grab your gnome then join the Vort and Alyx on the lift.
11. Follow the corridor to this clearing where you'll finally obtain the pulse rifle.
12. The vehicle you're after is on that bridge. Vort wants you to retrieve it, which means you'll need to jump it across the gap.
13. If you quickly zoom in you can get a fleeting glimpse of G-Man. To avoid a lot of gnome babysitting, toss your gnome so that he lands on the bridge near where G-Man was walking. Save your game before you throw the gnome just in case you miss.
14. Pass through this door after Alyx deactivates the force field.
15. Climb the stairs then use your Gravity Gun to reveal this shaft. Drop down.
16. Keep your Gravity Gun equipped to clear away some planks, drop to this area then clear away the boxes blocking this hole in the fence. More boxes block the exit door, behind which are many toxic head crabs and a toxic zombie.
17. Remove more planks then drop through the floor to this lift. Blast the trap door then drop through. More toxic head crabs are below.
18. Enter this stairwell and allow Alyx to snipe this zombie.
19. Exit the stairwell then drop below and approach those supply crates. Try to grab them with your gravity gun, but avoid the barnacles and the precipitous drop.
20. More barnacles are through here. Feed them explosive barrels then blast them with your pistol.
21. Remove these boards, then carefully walk the lone floorboard which remains after the barnacles remove the others.
22. A pair of flaming zombies make it through the fire. Turn the gas off with the crank to the left and the flames will subside.
23. Eliminate this zombie at the bottom of the stairs then open the door and wipe out a nest of sleeping zombies with a grenade. Grab the supplies before descending the stairs further.
24. Find a supply crate then get ready for this fast zombie hiding in the blue dumpster. I tossed in a grenade but he threw it back!
25. Shoot this padlock then proceed through the gate.
26. More zombies are on the other side, but Alyx has you covered.
27. Slip through the crawlspace seen on the right then battle more zombies, with Alyx's assistance. I found the toxic head crabs to be most troublesome. I'm using the SMG in this shot but I recommend the revolver for a one-shot-kill.
28. Descend these stairs once the zombies are cleared out. Ammunition can be found on the landing to the right.
29. Stay clear of this locked door. Zombies will alight the explosive barrels then come charging through.
30. Watch the barnacles munch on zombie-chow then beware a toxic zombie that bursts through the boarded-up doorway at the rear. A supply crate is between a pair of pipes on the right.
31. Ascend the stairs then find supplies (including grenades) in the red shipping container on the right before continuing up a ladder to the left of the impaled body seen ahead.
32. Find medkits at the top of the ladder then use your Gravity Gun to remove the metal sheeting blocking Alyx's shot of the zombies below.
33. Avoid dropping below until you and Alyx have taken out as many zombies as possible. More will emerge once you are on the ground.
34. Lots of zombies are behind this fence. I recommend tossing a grenade or two before they get too close.
35. Clear the area of supplies then exit through here.
36. Advance through this crawlspace and defeat this fast zombie. Shotgun ammo, a supply crate and a pair of barnacles are ahead.
37. Notice how you can ascend these shelves like stairs. The exit is that air vent at the far end of the room, but the final jump is just too far.
38. If you place a crate on the forklift, then raise it by using the red lever, you'll create a platform on which you can reach the air vent.
39. Here's how it looks once in place. Beware the toxic head crabs up here.
40. Follow the vent to a supply crate in this clearing. Take a look at the gap in the bridge you'll need to clear.
41. Carefully drop onto these pipes in succession to avoid damage.
42. Toxic sludge and zombies. Alyx's sniping skills are much appreciated. Hop across the islands of safety within the sludge to advance.
43. Yikes. Arrive on this ledge then climb the ladder ahead/right.
44. Find SMG grenades, shotgun ammo, a supply crate and this medkit. Drop over the ledge ahead.
45. More sludge. Climb the pipes on the left to jump across the sludge to the supply crate on the right.
46. Hop across the cars then maneuver these wooden wheels to act as stepping stones.
47. You can repeatedly move them to advance all the way across the sludge to the ladder seen here.
48. Plenty of supplies and plenty of danger are in this shack. A head crab, fast zombie and suicide zombie attack.
49. Climb the hill to the bridge. You're almost there.
50. Here's your car. A portal storm damages the bridge further, severing it just beyond the car.
51. Unbox the supply crate, then use the ladder to climb onto the railing (inset).
52. Walk along the railing to reach the raised section of bridge.
53. Use your Gravity Gun to push the cars at the lower end of the bridge to the higher end. The shifted weight on the bridge will cause it to teeter in the opposite direction.
54. Climb the railing from the opposite end and sprint-jump across to the original bridge segment.
55. Get in the car and give it all your gas and turbo to jump across the two gaps in the bridge.
56. If you threw your gnome onto the bridge earlier, he'll be waiting for you right where he landed. Go ahead and put him in the car.
57. Alyx and the Vort are up the stairs on the left, but you'll need to climb the ladder on the right to open the door blocking their path.
58. Use this switch to open the door, which closes very quickly. That's why it was necessary to throw the gnome onto the bridge.
59. Crack open this supply crate while the Vort opens the tunnel gate. Drive through to load the next level.