This chapter consists of Gordon Freeman entering the core to help slow down the meltdown. Afterward, they make their way to one of the still running Razor Trains and begin their journey to escape the city.
Later on, Gordon and Alyx are successful in re-engaging the reactor's containment system, delaying the explosion. Alyx subsequently discovers that the Combine are trying to use the reaction, and therefore the destruction of the Citadel, to send a message to off-world Combine forces. There is also a message from Judith Mossman, from an arctic environment north of City 17. She is talking about a Project which she and her team had discovered, but the Combine attacks the base and she had to cut the transmission. She is able to run away, presumably to safety, before Combine troops, and an unknown enemy invade the area she had been filming in. Alyx makes a copy of the message packet to take to Dr. Kleiner and Eli, ensuring that the Combine make them their prime target and even in their disorganized state use everything they have to stop them.
Alyx and Gordon then board a Razor Train to escape the Citadel. It becomes apparent that the carriage Gordon and Alyx are in was being used to transport Stalkers. Alyx mourns for the Stalkers and is then interrupted by the train derailing, which wakes the Stalkers.
