Half-Life 2 Walkthrough -> Intruder #1
After the armored personnel carrier explodes, head to the other end of the street, where Doggie will push aside the metal barriers and allow us to pass.
We enter the alley and through the breach into the building. In the far right corner there's a TV where you can see the G-Man for a few seconds, and in the near left corner, before the elevator, is the passage we need (you don't need to use either the stairs or the elevator).
Resistance
We emerge into a familiar courtyard. We were here almost at the very beginning of the game. We shoot down two Type II scanners (they have an assault rifle in their arsenal, in addition to a flash) and, together with the girl, we head to the station square, following Wallace Breen's voice, practically the same way we got here at the beginning of the game.
Having dealt with the monitor, the rebels happily accept us as their commander. Now we'll be fighting not alone, but with a squad of rebels. It's worth mentioning right away that the squad can be controlled. Although there are only two commands, they are sometimes necessary to save the entire squad.
We go right from the broken monitor to the metal barrier between the Baltic café and the Souvenirs store. After a while, the passage will open, and several Metrocops will appear. The rebels are mortal and weak, so we take the initiative and, if possible, eliminate all the soldiers ourselves. Of course, they will help us in this, but this help is rather weak, and hiding behind their backs, you can lose even this help.
Explosive headcrabs
At the end of the street, turn into the archway on the right. You'll have to throw away the furniture—otherwise, our squad won't get through. A Metrocop will appear in the window opposite the archway. A Lambda sign on the left means the door to the building is closed, but there's a hatch on the left, covered with a sheet of tin. Then, turn left and emerge into the next courtyard. After clearing it of Metrocops and mines, head to the far left corner—the entrance to the building is there.
Upstairs, there's nothing but two zombies, a watermelon, and a TV with Brin playing on it endlessly. So, you can go straight to the street. We need to get to the end of the street on the left, but there's no way through the road, so we go right past the fire and into the corner where there's a passage inside.
At the end of the street, without thinking, we go into the building on the left, climb up, and jump back down. We emerge just beyond the barricade. From here, shooting the metrocops is much easier. We climb the barricade, and then even higher, and enter the building. In the room opposite, there's armor, then turn left. No need to climb up—there's a turret there, so we drop down.
Clear all the rooms of metrocops and drop down to the floor below. We repeat the procedure and drop even lower, into the basement. There are three turrets in the basement—two are immediately visible, and the third is hidden on the left.
It's best to kill the zombies under the floor before jumping. After jumping, first go up to the street. Behind one of the bars is a lambda sign, and next to it are three boxes of ammo. You can take them out with the gravity gun. Then we go back down and continue on.
At the end, on the left, we climb behind the netting and knock down the lock securing the net door so the squad (if any remain) can follow us. We emerge onto another section of the road and clear it of manhacks and metrocops. Behind the rubble is a medic who can blow up part of the rubble and create a passage. To do this, first approach the gap so he can see us, then back away and fire back at the manhacks and soldiers.
We use the machine gun for this, although the gravity gun may be more effective against manhacks. After the explosion, we pass through the resulting breach. The door on the left is closed. "Probably blocked from the other side," explains the medic-demolitionist. We'll have to go around and open the door on the other side.
There's some armor in the crates; it'll come in handy. On the wall to the right are the same drawings as on Route 17 near the gas station. We make our way to the far left corner. From there, we crawl along the thin white pipes into the ventilation duct, drop down into the corridor, and proceed to the closed door where a medic-demolitionist remains. We open it, and with what's left of the squad, we climb up to the street.
Stopping to shoot the Alliance soldiers from the windows isn't recommended. There are a lot of soldiers, and hitting them from a window is quite difficult. It's better to go through the rooms, climb up, and jump down through the hole in the floor. We go down and go outside:
There's no need to stop either—we'll still have time to kill all the soldiers. We enter the house on the right and climb to the very top, shooting the soldiers along the way, then pass another hole in the floor. An ally in the opposite house will lower a bridge for us, but another soldier will also come running—we greet him as expected. We go, descend, and climb up to the headcrabs. A fast zombie is hiding around the corner to the right. After shooting it, go into the hole on the left.
We jump down three floors and exit outside, but not through the closed door straight back where we came from, but through the open doorway on the left, into the courtyard, where the Alliance soldiers are. We go around it and re-enter the building. It's easier to climb up the rubble by going counterclockwise around the charred room.