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 removes a problematic part of a puzzle in one of the maps. While not necessary to download this in order to play the mod, I highly recommend it.
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.