1. Heal at the medical station on the left.
2. Your crowbar dispatches these CPs and clears the boards from the door ahead. Grab a 9mm pistol from the fallen CPs. Finally - a real weapon.
3. Battle two more CPs as you make your way up the stairs.
4. Once this train pulls into position, hop on and make your way to the indicated platform. Climb the short ladder and more CPs fire at you from behind.
5. Bust your way through this doorway.
6. To your left is health and ammo. Note the lambda graffiti on the wall -- these symbols will indicate supply caches and the path to follow.
7. Shoot out these barrels to clear the doorway.
8. Open this gate and shoot more barrels to take out the CPs ahead.
9. More health and ammo is on the ground here. Hop over the broken fence behind the white barrel.
10. The lambda directs you into this crawlspace. Grab the supplies inside then knock over the grate to exit the shaft.
11. Follow the opening in the fence to drop below here. Land on the pallet to break your fall, then head right.
12. Dodge or shoot the flaming barrel that the CPs roll your way. Find an energy power-up to the left of the stairs. Once above, note the health station visible center-left.
13. If you don't climb the stairs quickly, you'll have to dodge this oddly-thin train.
14. You'll want to take out these guys on the tracks below or else they'll follow you in pursuit. Note that you can shoot through the blue force field. Continue up the stairs on the right.
15. Your zoom assists in spotting these guys to your left -- unfortunately you cannot fire while zoomed. Backtrack to retrieve their supplies after you have defeated them. Another trio attacks, providing more supplies.
16. Health and energy are atop these crates. Bust through then descend the stairs beyond.
17. Drop to the tracks then heal at the health station seen here. Bust open the crates for more supplies. Follow the tracks a short distance to an open gate on the right.
18. Hop down to the canal, then advance through the bent bars ahead, then two more just like them.
19. Climb the ladder on the left, then drop into the shipping container through an opening in the roof.
20. A medkit is inside, along with this lookout for the underground railroad and his Vortigaunt friend. Before the lookout sends you on your way, the Vortigaunt charges your suit.
21. Bust through this pallet to load the next map segment.
22. Once again, use your crowbar to bust through.
23. Crouch and keep right under the debris, just in time to witness this barnacle gobble up a crow. Ready your pistol.
24. Stay left until clear of the debris, where you'll come to this large area swarming with CPs. Keep right to enter the indicated sewer opening. The other opening is locked.
25. Take out this CP plus his buddy farther left.
26. Health and energy can be found on the ground. Listen to the radio on the right for underground railroad chatter before climbing the ladder ahead.
27. Catch these two unaware then take over their mounted gun.
28. Clear out the area and an RPG-wielding armored truck opens fire. Its rockets are not very accurate and you should have no trouble dodging them. Drop below to recover supplies. Note the barrel on the right.
29. Shoot the barrel and the platform drops into place, allowing you to walk along the ledge ahead.
30. Follow the ledge to the tunnel below.
31. The lambda on the left wall clues you in to a crate past the front of this red station wagon. Bust open the crate to find two medkits.
32. Continue through the tunnel. Barnacles block your path but most are easily avoided.
33. Spy another railroad subversive who guides you to the sewer entrance on the right.
34. Hoist yourself onto the ledge from the left side as indicated. Enter the next sewer tunnel.
35. CPs toss flaming barrels from above. Remain underwater until they explode. Two crates floating in the water hold energy cells.
36. The explosions have ripped an opening in this next passage. Climb on in.
37. Emerge in this clearing. Shoot the barrels to clear the way and defeat the CPs on the bridge. A supply crate off-screen to the right holds an energy cell.
38. Defeat two additional CPs then use your crowbar to knock aside a barrel under the indicated archway.
39. Proceed with caution. The ground is slippery and barnacles are aplenty. If you want to get fancy, toss a flammable barrel and shoot it to explode once a barnacle has lifted it. If a barnacle does get hold of you then shoot it or beat him senseless with the crowbar. You want to proceed up that dirt pile on the right, where you'll find health and energy.
40. More barrel-tossing CPs ahead. Again, remain underwater until the barrels explode. Use the indicated ladder to hop over the obstacle.
41. Emerge up the ramp on the left. Supplies are near the body. Hop across the boards to enter the tunnel on the right and load the next map segment.