The mission begins with Miller and Ulman discussing the Kiyevskaya station, which they may have to passs through to get to D6. During this time, you will experience another vision involving the Dark Ones.
Once you are revived, you will arrive at the airlock, with nosalises approaching from behind. Man the flamethrower turret, and attack them as they approach. The nosalises will jump from wall to wall, alternating between the left and right sides. They are somewhat vulnerable on the nearest wall, with the flamethrower being able to kill the nosalises just as soon as they leap. If the nosalises reaches the train, they will attack you directly, but within the firing arc of your turret.
Search the room on the left for ammo and filters and follow the rangers.
Flip the breakers on the right hand side of the door.
In the dark tunnels, Nosalises will attack from the vents. They will engage in waves for each room you enter. You can advance each time the attacks stop, when you will eventually reach the door at the end. Once you reach a door, a final attack will cause Boris to get killed, where you can retrieve his weapons and ammo.
When the map is loaded, check the room to the right for ammunition.
Once the door opens, wear your gasmask. When you enter the next room, you will be attacked by a large wave of nosalises. They will attack from a vent in the dark corner, and throwing a grenade should take a few of them out. The second major wave of nosalises will try attacking Vladmir, who is at the front of the group.
Once the two waves are cleared, follow the rangers. They will stop at another set of doors and start to open them. When you get through, the door falls, cutting you off from the rest of the team, and place you near a plated nosalis. This enemy can be killed by up to 20 military grade rounds (or shotgun blasts), but is also repelled by pointing your flashlight at it. It will also drop from the ceiling and attack from behind. You can also break open doors in this area and collect military grade rounds.
At the end of the room is a short run in a sewer, where you find and run up a ramp. You may take off your gasmask, but will encounter another plated nosalis. You may collect ammo on the ledges above, but to continue, go to the walkway and walk into the tunnel, where you find a breaker to open a door.
You are now reunited with your team, and an automated train will arrive to bring you to D6.
You are arriving at station D6, which has a thick gas. In the train, you can collect some ammo at the back. Once the train stops, follow the leader to the control room as he walks through the trains. When instructed, head to the top, and open the four covers. You will be told to press buttons to restart the vent system. These will be identified by number or by a red strobing light. Approach them, and hold the button down until the motor starts.
Once the gas starts to clear, you may return to the control room. If you see a greenlight on a wall keyboard, you can press it, then use the nearby screen to activate turret (which is out of ammo and can't fire.) Follow the rangers down the lift.
The door to the command center is closed, but can be opened by waiting, or by using the cart to the right. Follow the rangers inside and collect the ammunition found within the small room, and in the shelves on the right of the command center. However, there is insufficient power and the reactor has to be restarted. The trip outside involves the first encounter with amoeba. They mill mostly focus on miller, but may still attack you if you are close. Amoeba are easily killed, but once they stop, they are invulnerable and will detonate.
After going down the first lift, you will have to get through a corridor filled with amoeba. To destroy them, fire three shotgun shells to each amoeba pore before they attack. If you have a clear shot, you can also snipe the pores from the floor above using 9 bullets of military ammunition.
Thisis also the last chance to use grenades.
This level starts the same as the last one. You have to go through a gauntlet of amoeba pores, which attack almost as soon as you leave the lift. You can destroy some of the pores by shooting through the chain link fence. Before climbing the ladder at the end, be sure to collect supplies from the two shelves found on the outside of the lower level.
Once you reach the ladder, climb it. You will start the reactor activation process, but the biomass will intervene. Exit by the right door and climb down. Run across the reactor to the opposite side, and climb up. Enter the crane, and move it above the three contact points and lower the crane. When it connects with the rod, it will injure the biomass and raise the rod to allow the reaction to start.
When all three rods are extended, return to Miller. He will go to an alternate lift back to the rest of the team.
Collect all ammunition and filters from the crate, as well as the laser guidance system before continuing.