Alyx will be pole dancing to Brittany spears 'Hit me baby one more time;' while Eli is taken by gman to his crib. Kliener then tells you Barny got Stuck in a lift and you got to back the way you came in ep2 and half way through ep1. ep3 will be going back to White forest, again.
But really, it will likely begin with the minutes after Eli's death and vortigaunts, carrying his body to a place. Maybe they will wrap him in a shroud. ALyx is crying, then some stuff is said, 'get to the choppa' go to the Borealis, Alyx goes with you and is sad but very angry and throughout, your chopper gets mauled by the same adviser that killed Eli, Alyx see it and gets very pissed off, so she goes off running after it, then some deep ice fissure opens she falls, so do you. Then its a bit like the Antlion caves only you got advisers, then you get to the borealis, stuff happens, you find out the secret, turn on a big machine, then 'shwooourrp' something happens, like teleportation or portals open, advisor's stream out and other epic shaz, and the gman stop in to say Hai, fade to black... roll on the finale.
I do believe honestly something along those lines it will pan out, nothing is quite that straightforward in HL2 world, you see the path clear ahead then suddenly a beam falls across it. Same with the chopper likely to crash, otherwise they'd fly straight to the boat, and you can't be sat there for an hour, as your seeing it through Gordons eyes and passage of time.
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