After a short conversation, follow your friend through the next couple of doors until you reach a larger room. Interact with the vehicle when prompted to do so and use the on-screen prompts to get it started and moving. Be sure to switch those lights on too!
Ride the vehicle down the tracks a short way until you see an open doorway on the left. Hop out and climb the stairs here for a Morality Point . On the desk you will find + 5 Military Grade Rounds and on the ground near the bed an Accordion [Instrument 1/1] . You can open the lockers in here as well for some Throwing Knives, +5 Military Grade Rounds and some ammo. Return to the vehicle.
Proceed a little further along the tracks and you will spot another door on the left. Hop out and grab the Filters from the cabinet on the wall here. Enter the door.
Go straight ahead and loot the corpse for a Medkit and some ammo and follow the tunnel around to the left (note that this is a circular tunnel that will ultimately end up back at the entrance). You will have noticed the webs and the eggs everywhere. That’s right; unfortunately we are in another spider nest. If you move through the tunnel here slowly, you should be able to pick the spiders off one at a time as they come to attack you. Do not rush as fighting off 2-3 of the spiders at a time can be quite difficult even on normal.
I counted a total of 13 spiders on my way through the tunnel system here. There were also three corpses in the main tunnel, each with a Filter and ammo . Around halfway around the tunnel, you will find a small side passage with red lights in it. Enter for a Morality Point . At the end of the red tunnel is a corpse with some ammo and a Custom Weapon and an ammo stash on the ground to his left. Next to him is a panel that we can interact with to restore power to the spider tunnel, making lights appear to keep the spiders away.
Activate the panel and return to the main tunnel. Hop back into the vehicle and continue along the tunnel until you reach the next open door on the left. This is a semi-flooded room and the entrance is marked by some of those glowing green mushrooms so it is hard to miss!
Use the switch in the first room to turn on the lights in the next larger room. Proceed inside to find a Custom Weapon on the floor here and at the far end a small side room with a locker containing +10 Military Grade Rounds and ammo and a desk with Throwing Knives , a Filter and some ammo on it. You will also receive a Morality Point for exploring this area. Backtrack to the main tunnel, fight off the spider that appears if necessary and get back into the vehicle.
Ride along the track until you reach the large door blocking your way forward in the tunnel. Hop out and check out the room on the right. There is a Filter you can grab in the cabinet in the wall here. Continue inside.
As you enter, there is a corpse on the ground in front of you. Loot it for a Medkit and some ammo . On the wall to the left of this is a lantern that we can turn on to keep spiders away. Proceed into the next room and prepare to be attacked by spiders.
Similar to the previous spider-laden tunnel making your way through slowly is the best way to go so that you only have to deal with a single enemy at a time (I counted 9 in total). Work your way around to the right and through the tunnel into the next slightly larger room. Along the left hand wall in here is another lootable corpse (ammo + Filters ) with a lantern on the floor next to him that we can turn on to create a temporary safe haven. In the short tunnel that follows this is another corpse below a glowing green mushroom that we can pillage for ammo and Medkits .
After looting that, follow the tunnel all the way to the end to find another hallway with a red hue. At the end of this you will find a panel that we can interact with to restore power to the tunnel.
Backtrack to the vehicle tunnel and head over to the obstruction on the tracks. Throw the yellow switch on the wall to open the door. Go through a short way and hop out of the car.
Just before the branch in the track, hop out of the car and throw the switch on the left. This will change the direction of the track. Use the car to ram down the wooden barricade. This action will reward you with a Morality Point. In the area behind the barricade in a small alcove to the left is a corpse that you can loot for some ammo, Filters and +10 Military Grade Rounds . Through the open door on the right are a Custom Weapon and a corpse with ammo and another +10 Military Grade Rounds . Get back in the vehicle and go back and switch the track over.
Ride the car to the left this time and continue along until the next fork in the tracks. Hop out and check out the left hand track here. Loot the corpse for a Filter and some Military Grade Rounds enter the damaged train car at the end of the path. Follow it all the way to the end for a Morality Point . You will also find a corpse holding onto +15 Military Grade Rounds , ammo and an Incendiary Grenade . Backtrack to the vehicle, killing the watchman that has spawned behind you as you go.
Hop in the vehicle and ride it down the right hand fork this time until you reach a train car on the tracks in front of you blocking the tunnel. Get out, grab the Filters from the cabinet on the wall next to the open door on the right and then enter the room.
Follow the hallway to the left and kill the 5 watchmen in this room. Continue around the corner to the right. Duck into the side room here to find a Custom Weapon . Return to the previous hallway and at the far end, look over to the left and kill one more watchman here and loot the corpse for some Filters and ammo . Head back to the vehicle.
Move the vehicle forward and you will start to push the rail car on the tracks here forwards slowly. As you do, a number of watchmen will start chasing you up the tunnel from behind. As such, hold down the movement button to keep pushing the train car, but look around and start shooting at the watchmen as they approach. If they jump on the car, they will start to do you some serious damage so get them off as soon as possible.
When you see an opening on the right (if you are looking backwards), kill any remaining watchmen before stopping the car and hopping out. Continue all the way to the far end of the room and loot the corpse for a Custom Weapon and the lockbox nearby for some Medkits .
Note: During the next sequence you will need to move along the tunnel whilst defending yourself from watchmen. If you can kill them all before they jump onto the vehicle you will earn the achievement/trophy 'Scram'. To do this more easily, make sure to switch your ammo to military grade rounds for extra damage output.
Return to the vehicle and continue pushing the train car. Again, watchmen will appear behind you and chase you up the tunnel. Keep them away until you see another open door on the left (if you are looking backwards). Kill any remaining watchmen and pop out and enter the tunnel.
Follow the flooded tunnel to the far end and continue around the corner to the right. At the end you will see a watchman here. Kill this hairy beastie and an additional 5-6 of them will show up (3 form the front and 2 from behind). Backtrack through the room towards our vehicle whilst backing away from them to take them all out. Once they are all dead, check out the dead end where we saw the first watchmen to find Diary Note [Note 1/1] . There is also a corpse and a lockbox to loot here. You will also pick up a Morality Point for exploring this area.
Return to the vehicle and kill the two watchmen that attack along the way. Continue pushing the train car. Again, watchmen will appear behind you and chase you up the tunnel. Keep them away until you reach the next fork in the tracks. The train car will head off to the right.
Get out of the vehicle and switch the tracks to change the direction to the left. Hop back into the car and drive the car through the wooden barricade there. Continue along the tracks until a scene plays to end the mission.