When it's done go to the communication room. Alyx will contact White Forest.
When the transmission is over, get back to the car and head towards a gate.
Follow the road until you get to a building. Park the car in such way, that the building with a broken roof is to your left.
Get off the car and search the buildings to your right. Your consciousness will get disturbed somehow. When you search all the buildings get inside the one with the broken roof.
Go to the end of a corridor and turn left. Remove the padlock and keep going. You will see that there must have been a battle inside this building.
Take any supplies and get inside a whole in the floor. Go straight ahead. Collect any goods on your way. You will get to the stairs.
You will get inside a barn. It will be some kind of a breeding room for a creature that feeds on human brains. Alyx will say that it still can be killed. To do so you will have to shoot a few times in a blue energetic beam. Use the gravity gun(LMB).
After it's done, the creature will.. free itself. You will watch a cutscene. The creature will be wounded and will get away.
The Combine soldiers will show up. When you repulse the first wave, get outside.
On your way you will find a crossbow. When you're near the exit, soldiers will show up again.
When you kill all of them, run to another building. There will be some soldiers and a hunter. After dealing with them, get back to the car and hit the road. Try not to stop.
Stick to the road. Then turn left and you'll get on a railway. Get between the wagons and hit the pedal to the metal. Watch out for the bombs dropped from the chopper. They go off after few seconds.
When you pass a tunnel get to the left side of the road and keep driving.
When the tunnel is over, do a U-turn and drive left to another tunnel. When you pass the bridge, head right towards the red barriers.
You will get to a fence with a logo of rebels on it. After you pass it your car will brake down.
Get out of the car and head to a tunnel.
Keep going until you get on a yard. There will be a chopper flying above.
The chopper drops bombs that go off after a couple of seconds. You can grab them with the gravity gun (RMB) and throw them at the chopper (LMB). Do so do destroy the chopper. Grab them as soon as they touch the ground. Couple of shots and the chopper will crash.
To restore your health level go to the building shown on the screenshot. You can also recharge your armour there.
Get back to the soldiers and listen to what they've got to say. When you get to a building, new chapter will begin.