After the long train ride, you will drop off just before the large underground section. You will then need to proceed on foot to sneak across or fight through a battlefield.
For the stealth route, head forward and keep to the left. Walk down the stairs, and head to the left track. You should overhear soldiers to the right talking about a secret passage. Wait for the conversation to finish, and for the officer to depart. Once he leaves, you can sneak past the other guard, hiding on the right-hand side of the pillar before jumping over the rail.
After getting across, head to the left for the first walkway, walk across the pipes until you reach a horizontal beam, and walk across it to the right-hand wall. Follow the arrow pointing up, and the arrow pointing across. You can find a gasmask if you have a cracked one, but the rest of the trip will be below in the poisonous fumes. Climb down onto the pipe and reach the bottom.
As you approach the manhole, look for tripwires. If you step on one, either run back, or bolt forward as fast as you can. When you reach the manhole, look for a ladder on the right. Climb two ladders, and you are now behind enemy lines.
The first enemy room has three Nazi guards. Wait for one to approach from the side passage before heading to the spiral staircase. When you reach the top, look for broken glass at the corner just before the doorway to the main tunnel. The main tunnel is patrolled by two guards, as well as a trolley that moves back and forth, but there is enough cover to avoid detection.
At the first Nazi camp, hide behind the sandbag wall at the top of the stairs on the right of the tracks. Wait for the trolley to approach the front line, and you can sneak into the tunnel behind the camp. Enter the rooms to the left, collect any ammo, and open the final door to start the next section.
You were captured, but quickly get rescued by rangers. Collect the ammo from the dead fascists (a silenced revolver is available here), and follow the rangers to the Armored Trolley for a trip. You will be in the gunner's seat, protected by armor plating on the side. Use the movement keys or stick to rotate the turret, and you get a bit of aim with the turret in the given position. The machine gun has infinite ammo, but it overheats if you fire for an extended time.
When you board the trolley, you will approach the door. Honk the horn (with the use command) to continue. After a small advance, an officer stops to question the driver. He gets suspicious and starts the alarm, and the chase starts.
The first group of enemies will be from behind. They will be trolleys in pursuit. You can stop the gunner by shooting him directly, although the turret's armor makes it slightly difficult. If the gunner is killed, the driver may still try to ram you, thus requiring the trolly to be completely destroyed.
After the three trolleys, you will be attacked from the left by a large number of soldiers. Use the turret's armor to your advantage, and engage the soldiers one at a time, but be quick since your trolley can be destroyed. There will also be another trolley approaching, and that needs to be stopped as well. Once all enemies are defeated, turn towards the front, and destroy the obstruction.
After the barricade are a few soldiers in front, but more trolleys will attack from behind as well. After the first trolley will be a panzer that tries a quick shot at you. Next up are barracks in front of the tank, and the final enemy is an armored trolley, where the driver is protected against bullets. It will be shaken off when part of the tunnel collapses.
The final encounter will be the panzer. Once it pushes the train off the tracks, you need to shoot the supports under it. Aim for the support directly ahead and under the tank, that spans between the two tracks. Aim at the joint, and the platform will break beneath the Panzer.
You are still in the railway tunnels, but transferred to a different cart. You will need to keep watch towards the front for now, with both enemies and obstacles trying to take you out. You may want to use a silenced weapon, but a quick reflex has the same effect.
The first enemy will be a Fascist that calls an alert. If taken out quickly, you won't alert the other soldiers as you pass by. When you enter the station area, you can duck into the cart to avoid taking hits, but you are free to kill fascists as you see fit.
Once you reach Depot station, recognized by a large number of trains, you will attract the attention of nosalises. They will attack from all directions. During the battle, you will be knocked down, and Pavel will be pulled off the cart. The cart will accelerate and will eventually crash after outrunning the nosalises.
Once you stand up, you may enter the broken pipe, or explore the train. The train cart has wire traps on the left and right, which may be disarmed. There is also ammunition, in addition to a silenced revolver that you can take (if you don't have it already).
When you enter the pipe, heading right leads to a small ammo cache, and left leads to the next station.
Walk forward and speak with the captain. He will mention that there is an incoming attack, and to collect the remaining ammo from the cache. You are stunned by a sonic attack, which will soon be followed by a large number of nosalises.
Find a defensive position for yourself - the right corner seems to work, as long as you watch for enemies crawling on the ceiling and one the right. You cannot stop all of them, but engage the ones that fight you directly, or that attack other soldiers. If you survive long enough, another sonic anomaly will knock you out. Once you wake up, collect any ammo on the deceased allies, and speak with the Maxim once more. He will give you a tape, which you should take.
Enter Hole station. The entire population was wiped out, leaving only scattered supplies. However, there are a few supply caches you can use:
- In the first section, head straight towards the rail car. Pass through it (watch for a tripwire) and look for any useful items.
- In the first section, on the upper floors, there is some pieces of ammo. You may also find a medikit in the hospital as well.
- In the transition where you need to use a gas mask, you should find some extra filters.
- When you need to use the gasmask, look for a passage to the left or right. This should bring you to a supply cache after you cross a makeshift bridge.
- You may hear music in the background. Track down the source for some extra ammo.
With all items collected, continue onward. When you hear some crying, that indicates you are approaching the end of the station.
You meet with a child, who's uncle was killed. You bring him along with you, with the result that your aiming will be slightly slowed. The main enemies will be lurkers, who will attack in large quantities by hit-and-run attacks. However, the child will spot enemies for you.
After climbing the first ramp, you will see a tripwire. Jump over it. In the next room, Sasha will tell you about ammo found in the locker.
Proceed down the corridors. After the room with the loose ceiling, you see a branch, but can only take the left passage (the right leads to radioactive water). Jump over the tripwire, and climb up the vertical shaft.
Once you reach Sasha's mother, she will offer ammo as a reward. You may accept or decline it. You will be transported to the market, where you can get better weapons, or exchange ammo.
This is an outdoor mission, and requires a mixture of action and stealth.
Within the tunnel, there is a spare filter and gas mask that you should take. You can also collect ammo on the person on the left. When you proceed forward, you will hear Nazi guards making an advance towards the station. You can avoid them by making a hard turn right, and climbing the ladder. The patrolling Nazi on the catwalk can be safely sniped with the silenced revolver collected in Depot as long as he is at the far end of the walk and the other soldiers have went down to the surface.
Climb up the ladder above the tunnel. If you need filters, enter the building to the left, and quickly dispatch the two Nazi guards. You now need to approach the buildings, and if you alerted the enemies, there will be a rooftop soldier trying to attack you - he may be avoided by hugging the building's wall. When you approach the collapsed section, an unarmed soldier will run, and be grabbed by a flying mutant.
Enter the building by the collapsed floor, and head left. There are two fascist soldiers in that room, and killing them will attract other fascists from down the corridor. Head to the end of that corridor, and follow the arrow to get to the upper floor.
Once you are at the upper floor, you will need to kill fascist in the other rooms. Two are on the second floor, and two more are in the side room across from the ramp. If you want to play the radio message, climb onto the roof from the side room, and jump to the middle section of the third floor. Jump across the trip wires, and you should reach the radio station where you can play the tape.
You now need to reach Black Station. There are two ways to reach the ground floor. The safest way is to enter the side room across from the ramp leading to the upper floor. This room has a hole to the first floor, allowing you to more easily flank the fascist soldiers. If you are pressed for time, you can jump over the broken walls on the second floor - you will have more difficult here since enemies will flank you if you advance, but you can easily throw a grenade to take out most of them. Once the threat is eliminated, check the desk on the left hand wall for some filters.
Exit the building, and turn right. The entrance to Black Station is ahead behind the maze of cars, but there are some soldiers in patrol.
Ulman will describe the situation. He will get a ride ready for Polis, and you will have to travel through the station.
The front entrance has a few traps, a tripwire, and broken glass which are easily avoided.
The first two guards will talk about their homeland, and are distracted as long as you remain quiet. You can advance, and will come to a branch leading left or right.
If you take the left path, you will approach the generator. You will hear chatter about the generator being weak but will hold as long as nobody touches it. To reach the generator, sneak down to the first floor, and to the right of the soldier looking at the map. There are two guards watching the generator directly, one on patrol and one sitting down. If you can silently eliminate the soldiers and turn off the generator, the rest of teh station will be dark, making it easier to progress. If you proceed to the next room, you can find a tunnel leading to the right-hand side of the station.
If you take the right path, you have a faster path to the destination. First, listen to the guards talking about morality. Once the discussion finishes, they will move away, allowing you to sneak past. The destination is on the far right of the station, behind the gate.
After the gate are some more guards talking about a story, and one is directly watching the entrance. When you get past them, you can make a left turn and enter the hole (and wearing the gas mask). Watch for traps, and get through the tunnel to reach Ulman. Board the cart, and you will now reach Polis.
You will encounter a Dark One on the journey, in another dream-like sequence.