Train-wrecked is the fifteenth chapter of Uncharted 2: Among Thieves.
The flashback story catches up to the events in Chapter 1, A Rock and a Hard Place. Nate once again finds himself hanging off a mountain on a wrecked train, with a bullet in his side. After climbing up the hanging car onto a cliff, Nate then makes his way through the train-wreck he created. Along the way, Nate mumbles about his "heroic" acts trying to save Chloe. After Nate finds the dagger in the snow, he is forced to fight Lazarevic's soldiers. Injured and short on ammo, things are looking down for him, but he is able to kill them all by himself regardless. By the end of the chapter, Nate is shown trudging through the snow, eventually fainting, seeing only the blurred shape of what appears to be a human, coming towards him.
This chapter revisits the sequence from the first section of the game where you had to climb up the train as it's hanging from the side of a mountain. Climb up the train, much like you did at the beginning of the game to reach the top of the cliff. After you jump out of the falling train, the game will skip over to where the first chapter ended. You will now have to face three separate waves of enemies, a battle that will become increasingly difficult as the snowstorm around you intensifies. Fortunately, the gunshot that injured Nate will not have any effect on your movement in this battle, allowing you to move freely as you normally would.
Approach the lone enemy as you make your way further away from the cliffside and stealthily attack him. You may want to grab the M32 Hammer located atop the the fallen train car to the left of where you begin, as it will help later on in the fight.
As you continue further, clear the area of all enemies. Take out as many enemies as you can here before they see you and use the gas can in the middle of the area to take out a few enemies at once.
Keep maneuvering around the destroyed train cars, taking more enemies out as you do so. Beware of the three armored shotgunners, the last enemies you will face in this chapter. By now, the snowstorm has heavily obscured your vision, so not paying attention to your surroundings will allow them to take you by surprise and swiftly eliminate you in doing so.
Once the area is cleared, which will be indicated by the change in music and Drake remembering his injuries, make your way to a cliffside at the far end of the ruined train to end the chapter.
You cannot sneak your way to the cliffside early. Attempting to do so will result in an instant death.