Half-Life 2: Episode 1 - Chapter 4: Urban Flight - Finding Barney

The collapsed pipe lands in one very dangerous room. The whole room is wired to blow and it should kill you if it does. Freak accidents are possible. I once survived a full explosion with only a minor hit, but that’s a rare exception. You need to knock out the vent on the top of the pipe. and then pop your head out. Climb up and jump over to the barrels. Drop down to the bench and position yourself for a clear jump over the tripwires. You should be able to make it over without setting anything off. Hurry to the elevator and jump into it.

The elevator doesn’t work though and quickly sinks. Use the gravity gun to knock off the roof panel. Swim through the hole and jump out at the next level. Be careful, though. There are 2 barnacles above you and they like to grab you as you jump out of the water. If they start to pull you up, just turn around and shoot them with the pistol. If you want to do the puzzle right, you just have to crouch under the 2 tripwires and jump through the broken window. That’s boring though. Put 2 shots into a barrel and then duck below the water. Hop out when the explosions stop.

Kill the poison headcrab inside the little room with the broken window. Jump through the hole and then push the table to the left. Climb on top and go into the air duct. Climb up and come out carefully on a little part of the elevator support. You should be right back where you started, except on the rail. Be careful to not touch the barnacle tongue though, since it will drop you back to the lower level. Walk along the edge and jump over to the other side. Walk along it and grab the ladder.

Climb up and carefully get onto the beam. Drop down to the ledge on the right and knock off the vent. Crawl along until you come to the next vent in the floor. Drop it right through the tripwire to blow up most of the explosives before you drop down. Once the barrels stop exploding, drop straight down. There are still 3 hoppers in the room. Pull each of them up to disarm them. Then use the fuse box to unlock the doors and rejoin Alyx. Follow her through the next door.

Go forward with your gun drawn. Kill the zombie torso before it trips the mine. Then go forward and move the explosive barrel away from the next set of mines. Safely set them off from a distance with a pistol shot. Advance through them and look at the door. The Combine are preparing another breach. This one is pretty easy though. Just 3 Combine soldiers with shotguns and SMGs. Wait by the door and give them a good shotgun blast or 2. Go inside once they’re dead.

Grab the crossbow in the corner and make sure you break open all the supply crates. You should be able to find some SMG grenades. When you’re ready to go, use your gravity gun to pull the plug in the corner. Then head downstairs and go through the dead force-field.

Go outside and rush up the stairs. Try to pull up the hopper and reset it before the Combine rappel in front of you. Fall back down the steps and switch to the pulse rifle. Use it to start clearing the streets from the 5-8 Combine rappelling down. Push forward past the hospital to team up with a rebel with a rocket launcher. Look up and kill the Combine who chased the rebels across the bridge. Then move down the street. A few more Combine rappel down on this half of the road. Another group also do a door breach on the double doors at the end of the street. Just take cover by a car and help your allies pick them off. Move back up the street a bit to find a rebel on the side of the street. He can take you inside to the safehouse.