Half-Life 2 Walkthrough -> Dark Energy
Who unexpectedly helps
Breen, is in league with him, but out of her feelings for Eli, she tries to keep him alive. Breen has a different perspective. In this difficult situation, Judith now betrays Breen and saves everyone else, at least for a while.
Brin escapes, taking the Gravity Gun with him. We follow Alyx in pursuit. At the top, Brin forgets the Gravity Gun, significantly increasing our chances of victory. Brin attempts to escape by teleporting from here.
Citadel Explosion
So, we grab the Gravity Gun, replenish our health, and go down after Brin.
The plan is as follows: climb up and destroy the portal. We'll ascend, going counterclockwise around Brin (he's in the shiny ball in the center). The passage on the right won't open right away—we'll wait. Then we'll pass three generators, first knocking out the energy balls. Next, we'll climb higher on the moving platform and continue on.
At this point, the citadel begins to crumble, but time stops. G-Man stops it and says, "Time, Doctor Freeman? Has that time really come again? It seems like you've only just arrived. You've accomplished so much in such a short time. In fact, you're so good that I've received several interesting offers about you. Normally, I wouldn't consider them. But this is a very unusual situation."
Rather than deceive you with the illusion of choice, I will take on this privilege myself, if... when your time comes again. I apologize for what seems like a despotic imposition of my will, Dr. Freeman.