Half-life 2 Walkthrough -> Arrival
A Strange Dream and Dr. Breen
After a strange dream, from which you will be brought out by Mr. G-man (a strange man who looks like a half-ghost, half-dead man), exit the train car and stomp towards the huge screen, where an elderly man named "Breen" (the head of the city "City 17") greets everyone arriving in City-17:
Pass the guard (he'll be wearing an armored suit with a mask resembling a gas mask—they're called "Combiners"; there are three types of them, more on that later), who will rather rudely kick you in the chest, through the turnstile, and to the left, into the waiting room. A man at the table will advise you not to drink the water, saying they put something nasty in it.
An old friend...
Then a new guard will lead you into a side room, shouting, "Come with me, citizen!" When he removes his mask, you recognize an old man named Barney (the guard from the first game), and then you'll connect via video link on a monitor with Dr. Kleiner from the same first game:
It looks like these two are up to something. It also looks like the deception has been revealed, and enraged soldiers are about to burst into the room. Without further ado, exit through the next door, up the stairs, push the crate against the wall, and jump through the window (press "E").
You'll find yourself in a small nook, and you'll have to go through the door. The guard will ask you to pick up an empty can and throw it in the trash. What a neat freak he is, though, I don't want to mess with him, since I still have nothing to do with him.
Go outside and follow the only street not blocked by a high fence with coded access. Then turn right into an alley, where you can use the fire escape to climb over the bars. Turn right, and into the building on the left.
Escape from the Combines
Go up one floor and watch as masked men brazenly kick down someone's apartment door. People are hiding in the adjacent rooms, watching through the window as an armored personnel carrier pulls up to the building. Run down the hallway and up the stairs, and a man will call out to you from behind the door.
Immediately, you'll hear footsteps behind you, and a whole horde of Combines will rush in. Quickly run to the other stairs and back up again; a good comrade in misfortune will prop the door open with his shoulder, giving you a chance to escape.
On the roof, run to the paint cans. Behind them, there will be planks you can use to climb up to the ledge, which will lead you to an open window. Once you've climbed through, save immediately—I'll explain why in a moment. After saving, go down the stairs. The Combine will arrive and start beating you up.
Alex Vance
Don't be alarmed—that's how it was meant to be. When the fog clears, you'll see the face of a pretty young woman, Alex Vance.
When she takes us to the elevator, many people experience a glitch: she simply calls the elevator and doesn't enter it, just stands there. Load a save and the glitch should disappear. She takes us to Kleiner's lab, where we'll be unsuccessfully teleported later, but more on that in the next chapter, " A Great Day ."
Source: stopgame.ru