After climbing out of the sewer entrance, Calhoun finds himself back on the surface along a road within the facility near the southern exit of Black Mesa. However, the exit's been destroyed, which forces Calhoun to go the opposite direction towards the Black Mesa Trainyard. Along the way, the HECU end up shutting the entrance gate to the trainyard, which forces Calhoun to go through the nearby steam tunnel to find a different way out. Fighting through the Xen aliens that infested the steam tunnel, Calhoun finds a maintenance elevator that takes him up into the trainyard's warehouse basement. He then fights his way through the warehouse basement until coming across a couple HECU soldiers gunning down a scientist within the nearby office.
After disposing of the HECU soldiers, Calhoun checks on the scientist, who's been fatally wounded. The scientist, Harold, informs Calhoun of the bad news that using the freight trains to try to escape is a dead end as the HECU have been using the trainyard to kill or capture any of the Black Mesa employees that they come across. Harold further explains that the dead end is why he and a colleague of his, Dr. Rosenberg, came up with a plan to escape Black Mesa using the old prototype teleporter lab that's nearby. However, they were discovered before they could make it to said lab. In his dying breath, Harold assures Calhoun that if he manages to fight through the HECU to find Rosenberg, they will have a chance to escape the facility.
While fighting any HECU soldier he comes across, Calhoun passes by a small area under construction. He then takes the stairwell to get out of the warehouse basement, and gets back outside. Calhoun then breaks into the nearby freight train storage building where he kills the soldiers in the area, and manages to locate a captured scientist still alive in one of the freight cars. However, said scientist turns out to not be Rosenberg. Calhoun moves on to the nearby freight loading yard killing more of the HECU soldiers in the area, and locates another freight car holding a captured scientist. However, the second scientist also turns out to not be Rosenberg. Calhoun moves on towards the nearby freight car storage yard, but first has to pass through a train area housing an HECU tank. Thanks to the area's truck supplies having a rocket launcher, Calhoun is able to destroy the tank using rockets, and eventually makes it to the freight car storage yard.
Calhoun disposes of the HECU soldiers holding down the storage yard, and locates another freight car holding a captured scientist. As Calhoun enters the freight car however, HECU reinforcements arrive, and lock Calhoun in the freight car with the scientist. This time around, the scientist actually is Dr. Rosenberg, which Calhoun informs him that he knows about their plan of escape thanks to what Harold told him moments before his death. Rosenberg replies that what Calhoun claims is indeed the case as the plan is to use teleporter technology at the old prototype teleport lab to escape out of Black Mesa. Due to the top of the freight car they're trapped within having a ceiling vent, Rosenberg gives Calhoun a boost to jump out of the car, and get a jump on the HECU soldiers that trapped them in.
Once the HECU reinforcements are removed from the storage yard, Calhoun returns to Rosenberg. The scientist informs Calhoun that they need to return to the area that Harold died at as the access to the old lab was near there hidden behind some of the facilities new construction material. Calhoun escorts Rosenberg out of the freight car storage yard, and back to Harold's location while fighting any HECU soldier he comes across. Upon returning to the area under construction, Rosenberg points Calhoun in the direction of a newly built board wall claiming that the elevator to the old chamber is just beyond it. After destroying the wall, Calhoun and Rosenberg board the elevator, and ride it down to the old prototype teleporter lab. Calhoun can open the nearby security storage for supplies as Rosenberg puts his hand on the fingerprint pad to open the locked lab door.
Entering the old prototype teleporter lab, Calhoun sees that one of Rosenberg's colleagues, Walter, has been working to get its portal chamber up and running, but requires help on the larger equipment. Rosenberg brings Calhoun over to the main portal chamber room where another colleague, Simmons, is working. Rosenberg explains the problem that using old technology means that they can't make pinpoint locations for the teleport exits on Earth that they're required to make. He further explains that their development of teleportation is connected to a borderworld away from Earth, and that they developed a relay on said borderworld to provide the information needed to make teleports wherever they desire. However, contact with the borderworld team that made the relay was lost, which deactivated the relay. Rosenberg claims that the use of the relay became obsolete due to further developments with teleportation, but since they're using an old teleporter, they will need someone to go to the borderworld to finally reactivate the relay device. This person being Calhoun.
As Rosenberg works to get the old portal chamber up and running, Rosenberg explains the goal to teleport Calhoun to the borderworld as close as he can to the relay device that their Black Mesa survey team set up. Rosenberg warns Calhoun of the dangers of the borderworld, and that once they have confirmation that Calhoun has reactivated the relay device, they will create a new portal to return Calhoun to Earth. With the help of Simmons, Rosenberg works the old portal chamber machinery to create a teleport, which Rosenberg orders Calhoun to enter. Upon entering, Calhoun is sent off to the borderworld; also known as Xen.
This Chapter contains examples of:
- Backtracking: A part of the level requires Calhoun to escort Dr. Rosenberg back to the destructible wall housing the hidden elevator to the prototype teleporter chamber that Calhoun walked by earlier.
- Creator Cameo: When you're traveling through the tunnels before reaching the train-yard, in one of the side areas of the basement warehouse, there is an opened box that just so happens to have gear shaped objects spilling onto the floor. Aka, a gearbox. This is a reference to the Gearbox company that made Half-Life: Blue Shift.
- Developer's Foresight:
- You come across two scientists in your search for Dr. Rosenberg. If you actually try to backtrack with these two scientists following, there's a certain point in the office area that the scientists will refuse to go any further. You would come to realize that there is an invisible wall that will not allow the scientists to walk any further. Thus, making it clear that the developers made sure that the two random scientists couldn't be brought to the prototype teleporter chamber. That's because if you were able to backtrack far enough, you would come across the breakable wall that you would eventually learn about from Dr. Rosenberg that leads to where his colleagues are creating the portal device to escape Black Mesa. The reason for the invisible wall was so that you couldn't break the story and have two random scientists waiting at the elevator when Dr. Rosenberg leads you to it later on in the story.
- If the player destroys the wall hiding the elevator to the portal chamber before Dr. Rosenberg leads you back to it, he will have a different line-of-dialogue regarding the fact that Calhoun has already found the hidden elevator instead of the normal dialogue to destroy the wall.
- Escort Mission: Part of the chapter requires the player to escort Dr. Rosenberg back to the destructible wall that's hiding the elevator behind it that will take him and Calhoun down to the old portal chamber.
- Gas-Cylinder Rocket: Calhoun blows an opening through a locked freight-yard door by shooting the ends off a rack of compressed-oxygen tanks.
- Hostage Situation: Part of the chapter requires Calhoun to explore the Black Mesa trainyard to find the freight car that the HECU is holding Dr. Rosenberg captive. The first two hostages he comes across end up being random scientists while the third one he finds turns out to be Rosenberg.
- Just Train Wrong: Besides the typical Black Mesa monorails there are also a few conventional platform cars on standard tracks which are just a flat texture on the ground. Many of the cars are carrying containers but in real life containers are loaded on dedicated cars. Two of the cars are just stuck together with no clearance between them so you can't even see if there's a coupler between them. The cars are hardly wider than the rail gauge except a single platform car carrying a tank whichnote in turn is too wide to pass through the relatively narrow tunnels. There is a single yard with a turntable but the turntable can hardly contain a single car so it would require at least two switchers on different tracksnote but there is only one. Not that it matters much since none of the tracks seem to lead anywhere.
- Road Block: In a way. If you choose to go down to the old portal chamber earlier than you're supposed to, you can't enter said chamber without Dr. Rosenberg.
- Sequence Breaking: A very minor example, but the player can destroy the wall hiding the hidden elevator earlier than they're supposed to, and take the elevator down to the old portal chamber. While it's not possible to get in due to needing Dr. Rosenberg's hand identification to enter the chamber, Calhoun can still enter the security storage room outside it for supplies.
- Sidetrack Bonus: Several.
- The basement warehouse Calhoun traverses after coming out of the steam tunnel has several side areas off the beaten path that provides extra supplies.
- As mentioned in Sequence Breaking, if you reveal the hidden elevator and ride it down to the old portal chamber, Calhoun can enter the security storage room outside it for supplies.
- Unique Enemy: The HECU tank that Calhoun comes across in the trainyard is the only one that he ever comes across.
- What Happened to the Mouse?: The first two scientist hostages that Calhoun rescues end up just disappearing.
