Gordon and Alyx set off through the outlands to destroy a Combine controlled base, which is harboring a rocket capable of wiping out the Resistance.
This mod requires Mapbase, which has been included in the zip. If you already have Mapbase, you will only need to extract "What Remains"
Half-Life 2 and it's Episodes are also required, along with Source SDK Base 2013 Singleplayer.
1) Extract (all) the folder(s) into your sourcemods folder i.e. C:\Program Files (x86)\Steam\steamapps\sourcemods
2) Go to Source SDK Base 2013 Singleplayer on Steam, right click it and select "Properties"
3) Go down to the "Betas" tab, and select "upcoming" from the list
4) Restart Steam
What Remains should now be in your library, along with Mapbase.
Thanks for downloading! And many thanks to Blixibon for Mapbase, without it a certain feature in What Remains wouldn't have been possible for me.