1. Climb this ladder then exit out the gray door above (inset).

2. Ready your shotgun as you will come under attack from zombies and head crabs at close range and there's not much for your gravity gun to grab onto. Walk the planks to the rooftop ahead.

3. Jump across to this adjacent rooftop.

4. Drop to the ground here then head through the archway (inset).

5. Follow the lane left to this toxic zombie on the right. I found that two SMG grenades (alternate fire) bring down the zombie, then your SMG's primary fire cleans up any remaining toxic head crabs well. Rush up the stairs ahead then through the door at the top. Close the door behind yourself before another toxic zombie can catch up.

6. You'll find some much-needed ammo inside before continuing up this ladder.

7. Medkits and shotgun shells are on the left, and Gregori is on the right. Soon, toxic zombies will be climbing these two pipes. You can see the pipes shimmy as the zombies climb, making it easy to be prepared with your shotgun. Jon in Philly suggests staying close to the left drainpipe to lure the zombies up a single pipe.

8. Once Gregori's cart is in place, hop in and pull the yellow lever (inset).

9. Ride the cart to the other side, then hop out and grab the supplies from the table.

10. Father Gregori doesn't seem quite so insane up close. He offers to show you the way out of Ravenholm and tells you to follow him to the mines.

11. Periodically, Gregori will stop and fight along the way. He's invulnerable so let him tank for you and don't forget to check your six, especially while standing on this platform. (Update: Jon in Philly writes: "Father Gergori is NOT invulnerable. If you accidentally blow up a barrel next to him, he's toast and you lose. ")

12. This fenced corner can become a sanctuary or a death trap. The trick is to shoot the explosive barrels before entering. Once inside, grab the health and ammo and focus on the head crabs while Gregori takes down the zombies. More health can be found in the right corner outside the fence.

13. Follow Gregori to this spot where he'll raise the gate so you can slip under. Continue to the door ahead while Gregori battles the zombie hordes.

14. Yes, it's a jumping puzzle, and no, it's not as bad as it looks. Just stick to the outside and drop to the nearest beam below.

15. Don't miss those supply crates, and shoot out the explosive barrels to take out as many head crabs as you can. The entire area crawls with them.

16. Once you reach the bottom you'll find more supplies here.

17. Follow this adjacent catwalk to the mine shaft ahead. You can walk on the beams for a short distance to avoid the head crabs and clear the fence.

18. Move quickly and jump to the water below.

19. Swim for a short distance into a barnacle's tongue. If you wait until you are above these supplies to shoot the barnacle, you can use your gravity gun or jump to the ledge to retrieve them.

20. Jump below and climb over some beams to continue swimming and emerge here.

21. Throw the yellow switch to send the zombie chopper on its way. Be careful as it returns. The trick is to move forward and trigger the zombies to attack yet be out of the zombie chopper's way before it can chop you. There are several alcoves on the left where you can safely avoid the blades. Continue to the top of the shaft to load the next area.

22. Emerge from the mine shaft and find supplies here. A second supply crate is under the pallets on the left. Bullets can be had on the ledge under the lambda.

23. Walk left to find a medkit here.

24. Walk right and be attacked by this quick zombie. The expanse of track behind you makes for easy kiting. Just keep moving backward while shooting.

25. Farther along the tracks you'll encounter an Overwatch shooting zombies from this skyway. A well-placed grenade will bring him down.

26. Here's what he looks like. More grenades are in the supply crate seen here.

27. Be careful retrieving these supplies on the right. Another Overwatch sniper is in the skyway ahead.

28. After the logs fall off this train your path is blocked. Duck to crawl beneath the train and you can proceed.

29. Another grenade sends the second Overwatch flying.

30. Find more supplies on the tracks and from a boxcar on the left then stumble upon two more Overwatch troops battling zombies.

31. Grab a pulse rifle from one of their bodies or find one inside this box car with yet more supplies.

32. Next up is a firefight that you can largely avoid. Grab the supplies from inside this van then make your way as quickly as possible to the indicated doorway. You'll need to swing around some rail cars to the right to make it past the fence.

33. Once inside, help your comrades take down the remaining forces. I found the .357 to be the best way to quickly dispatch foes.

34. Another scripted sequence ensues. Look around for supplies. You are soon led to the door that leads to the next level.