On the ground floor of a residential building, Gordon is briefed by a rebel who was split up from Barney who informs him that his friend is now taking cover in a building down the street. He makes his way over to the building in question while taking cover from Combine snipers, then slips inside and fights his way past some zombies to get to the roof — what's left of it anyway.
There he meets Barney, caught in the crosshairs of the snipers, who nags at him to lob some grenades into their camping spots to flush them out. When all of them are finally dealt with, Barney leads Gordon to the Overwatch Nexus, a Combine stronghold situated in a large ornate building with a powerful mortar-like weapon sitting on top. He explains to Gordon that the mortar, dubbed the Suppression Device, is preventing the Resistance from pushing closer to the Citadel, so it's up to them to shut it down.
With that, the two of them lead an assault on the Nexus, dodging the energy beams launched at them by the Suppression Device. Once they make it inside, their next objective is to disable three generators to power down the Combine mortar while facing opposition from the Overwatch soldiers and ground turrets stationed throughout. Gordon is able to handle these generators with the Gravity Gun much like with the one he disabled with Alyx's help earlier.
With the Suppression Device out of the way, Barney sends Gordon to the roof of the Nexus to connect a skybridge to an adjacent building so that more rebels can make it through. After fighting off more soldiers and a Gunship, Gordon connects the bridge, crosses over himself, and descends to street level. A rebel informs Gordon that taking down the Suppression Device has allowed extra reinforcements to move in and tip the battle in their favor, and that there's a crate of rockets nearby he can use to arm himself to destroy an incoming wave of Striders. Dodging the Striders' fire, Gordon reaches the rocket crate, hunkers down, and takes down the tripod synths, and then sets forth along the last leg of his journey to the Citadel.
After evading another Strider by ducking into a building out of its sight, Gordon meets another rebel who tells him that the last few city blocks before the Citadel are going to be the most difficult to handle, as they're completely under the control of Striders. So begins Gordon's hardest uphill battle yet, which he manages to just barely survive by sheer luck and with the help of another crate of rockets at the top of a ruined building. As soon as all the Striders and a few Overwatch stragglers are taken care of, Gordon finally meets back up with Barney and D0g, the latter of whom has gone crazy trying to reach the Citadel and rescue Alyx himself. D0g lets Gordon through to the Citadel by lifting up a nearby razor wall, and after making his way in he at last finds himself at the base of the Combine star scraper.
This chapter contains examples of:
- Final Battle: The chapter ends with Gordon and his fellow rebels making one last push to the Citadel while taking fire from an entire squad of Striders.
- Pinned Down: Barney is initially found pinned down by Combine snipers, requiring Gordon to flush them out with explosives.
- Rule of Three: The Suppression Device is powered by three generators.
- Stealth-Based Mission: Done subtly towards the end of the chapter. After ducking down into a building to hide from a Strider, any Combine Scanners inside the building that spot you will sic the Strider into firing at you even without it having direct line of sight. It's possible to stay hidden from the Strider up until the very end of this section by destroying the Scanners before they see you.
- Unique Enemy: Inside the Nexus, Combine ground turrets make their only appearance in the entire game.
- Wave-Motion Gun: The Suppression Device protecting the Overwatch Nexus basically amounts to a high-tech mortar launcher that fires laser beams at its hapless targets.
