Half-Life 2: Episode One - 02 - Direct Intervention [Hard]

Chapter 2: Direct Intervention

Gordon and Alyx reaches the highly unstable Citadel Core to find it on the verge of collapsing. To stabilize it and buy themselves and other City 17 evacuees more time to get out of the city, Gordon must enter the core's chamber and re-activate the containment field.

Playlist with all completed chapters:
   • Half-Life 2: Episode One - Full Playt...  

Notes:
- Completing this chapter without killing any Stalkers will reward the player with the "Pacifist" achievement
- As shown in the video, Stalkers are completely neutral to Freeman if he doesn't attack them (2:14)
- If Gordon chooses instead to kill the Stalkers so that they won't disable the ball receptacles, one of the Stalkers will scream and start attacking him with its laser upon the first one's death
- To pass the hallway with the energy ball launchers (at 4:26 and 7:08), Gordon can also use the maintenance hatch door. Upon hitting the door, the energy balls will disintegrate

Trivia:
- Black Mesa, a fan re-imagining of HL1, contains a sequence in its Xen chapters that plays out very similar to this chapter, where Gordon has to activate three lasers to open up the portal to Gonarch's Lair
- The sound of the core expanding is the same sound the Thumpers make when repelling Antlions (0:36)
- Alyx telling Gordon to "hurry back" is very reminiscent of a similar scene in HL2's final chapter when she sends him down the elevator to the Dark Fusion Reactor to confront Breen (1:39)
- At 1:48, the HEV Suit voice says "WARNING. HAZARDOUS RADIATION LEVELS DETECTED". This is the first time in any of the Half-Life games that the HEV suit says this voiceline
- The core's chamber (1:52) is somewhat reminiscent of the test chamber in HL1 where Gordon activates the Anti-Mass Spectrometer
- The first appearance of the Combine Hunter at 10:09. This enemy will be encountered in person during the events of HL2EP2
- EP1's model of the Hunter is quite different from EP2's. It was formerly possible to spawn it in Episode One with the entity name "ministrider". This will reveal that the EP1 Hunter was incapable of firing flechettes (and fires pulse rounds like the Strider instead), has a grey armoured body, and no sounds
- The train at 13:00 isn't actually moving (as indicated in Valve's developer commentary at this section). Rather, the clever use of lights and shadows simulates the movement