After battling through an office complex filled with Vortigaunts, Adrian Shephard and other HECU soldiers' attempt to find and use an old transit system to escape to the Lambda Core. The Black Ops are first introduced in this chapter as well. Shephard comes across them in a hangar where they are loading a rock from Xen into the back of a truck. Adrian then learns that the Black Ops soldiers have been sent to kill the remaining HECU Marines and cover up the Black Mesa incident. Shephard meets up with several other surviving marines and fights the Black Ops, eventually reaching an underground railway system that leads to the Lambda Complex.
