On the following page of our Metro Exodus guide, you will read how to get to the wagon and tow it towards the train. This is quite a long task in Volga, which abounds in many events and meetings, among others, with a bloodthirsty, mutated fish.
First, get to Knyaz in the designated place and discuss the expedition with him. Then replenish your supplies and, if you want, sleep on the bed to change the time of day. It is also worth completing the above "question mark", free the prisoners and get the key, which will make it easier to get glasses with thermal vision soon.
Go to the place indicated on the map and then take the boat. Sail to the middle of the hangar until you reach the remains that won't allow you to continue your journey - go ashore. Go up the column and then go right. Try to follow the green lights that show you the way forward.
Kill the mutants and go further ahead. You will get to the door, the key of which you just had the opportunity to get (see above), open it, and then search the whole place thoroughly. You will find goggles with night vision, which will help you to comb through very dark locations.
Now go back through the door and walk through the scaffolding until you reach the lever, which moves the mechanism next to it. Continue with it and kill mutants. After some time, a giant fish will come to light and will knock you down.
Wear a mask and walk forward. Walk through the pipes and stairs further, fighting the next mutants. Go to the top of a large tank and then fight a new wave of enemies. Break through enemies and go down.
The road is quite simple - in case of problems with finding the path, remember to look for green points and use the compass arrow. Along the way, the giant fish that tries to stop you will appear several times.
You will come across more and more waves of mutants. Try to save ammunition and use Molotov cocktails to kill several enemies at once. Go through a narrow tunnel further and you'll end up on the other side of the hangar.
Use the reel to open the gate. Right next door you will find a lever that will clear the way to the railway trolley. Get into it and drive ahead to set off on the road and find the wagon you are looking for.
Before you finally leave the hangar, you can still repay the big fish for her attempts to kill you. Enter the room next to the open gate and you'll find yourself in a place with wires and a bell. Save the game - you only have one chance to lure the beast and use the wires to kill her with traps. This is described on a separate page of our guide.