Charge them with the crowbar and take them out. Here there are two citizens being attacked by two combine troops. In the hall at the bottom of the steps there is a heath station, press "E" to fill up and take a left down the next hall. Press "F" to turn on your flashlight and walk down the stairs. There is a dark stairway leading down to the left of the sign. Climb the ladder, turn left and jump to the next car and then jump over the fence.Quickly head in to the alleyway and walk towards the danger sign. This car has a ladder in it that leads to the top of the car. A train will be coming behind you, so scurry around the next car and turn back to the left and enter another boxcar. Smash through them with the crowbar, hop through the car and make a quick right. When you drop down into the train yard, make a left and hope into a boxcar filled with crates. You will have stay out of the open however, because combine officers will be firing at you. This is a maze of boxcars, and the goal is a hallway on the other side of the tracks. Walk straight ahead and use the crowbar to break through the pieces of wood blocking the next doorway. Hop down to the ground and walk behind the conductors to find a staircase.Barney calls to you from above and states that you are going to have to escape City 17 through the canals.
You finally appear outside of the lab in an area filled with electrical conductors. The Dr.'s head crab jumps into the teleportor and some unknown interference transfers you to a number of places including Wallace Breen's office. When it is your turn to make the journey, things do not go as smoothly. Throw the red switch to complete the process. You will have to help by picking up the plug and placing it back into the socket. Step into the teleport room and watch as Alyx is transferred to her father's lab. Notice that Wallace Breen has been scratched out of the photo of scientists from Black Mesa. There are also numerous items to be read and looked at on the walls. To the left of the entrance to the lab there is a small teleport machine that can be used to zap a plant back and forth between pedestals. On one of the settings, the G-Man appears waiting outside of a gate. On the monitor just outside of the room with the Hazardous Environment Suit, you can press "E" to change which camera feed appear on the screen. Charge the suit at the other end of the lab across from the bubbling vats.There are a number of interesting items in the lab. You now have a heads up display indication the suits charge power and the level of your health. Barney also enters the lab and you are given the Mark V Hazardous Environment Suit.
Look out for these markings throughout the game, they indicate the existence of hidden items nearby. Follow Alyx into the elevator and she will lead you down a concrete hall to a secret passage marked with the orange Lambda.