Half-Life 2: Episode One is the latest in Steam releases taking on the Episodic content system, while many may be a bit sketchy due to the freshness of this content delivery, it should be a given that if it's a series and part of the HL2 universe, you're going to need to play it to understand how things are developing.
Episode One drops players back into the Citadel area and gives them some company with the return of an even more prominent Alyx. While details of the espcae from the Citadel are not exactly clear the game leaves players with little time to really ponder that tidbit as the Citadel rocks the Earth as it comes back to life for a final hurrah. From here players have to scramble to get out of City 17 by any means necessary.
The game itself brings some updates, obviously running on the updated HDR enabled Source engine is the first. Players get a taste of what an even more detailed HL2 universe can come out as. For those that haven't experienced Half-Life 2 before, the game also brings in Half-Life 2: Deathmatch and Half-Life: Deathmatch Source to the table for a bit of bonus to the experience.
With that said lets get going into the world of Episode One.