When Half-Life 2 arrived for high-end PC distribution in late 2004, it brought with it the kind of experience many gamers were expecting from the likes of Valve Software. The game was fast, had you thinking quickly, and looked and played with a level of amazement that some people are still shaking off to this very day. But it followed a series of cryptic events that left a few questions unanswered, leaving some of you out there to scratch your heads and try to figure out things. Well, you'll have your answers soon enough when Half-Life 2: Episode One, a new expansion pack for the game, arrives this fall.

Originally called Half-Life 2: Aftermath, Valve has since renamed the expansion pack to kind of give the feeling that the story isn't going to be all wrapped up with this expansion pack release (in fact, I beleve Episode Two is already in the works). The game puts you back into the shoes of the troubled Gordon Freeman, whose successful assaulton the Citadel has some dangerous reprecussions. As a result, Freeman and his assistant, the beautiful Alyx, have to flee from City 17, but the task is not as easy as it looks, thanks to all sorts of freakish creatures that stand in your way.

The gameplay from Half-Life 2 will promptly make a return, allowing you to use weapons, ride vehicles, and pick up objects that will no doubt come in handy as launching weapons and opening up new paths. But Valve is promising that the gameplay will see a bit of touching up to challenge gamers a bit further, although they're a little tight-lipped in terms of how it will be done. They did, however, indicate that Alyx and Dog, another fighter working with Freeman, will be more heavily involved. Perhaps some kind of co-op opportunities will come into play...?

Valve is being nice with one thing, though. Episode One doesn't require the original Half-Life 2 to operate. So if you happen to not have it on your computer at the time of download or you opted to play through the game over on the Xbox instead, you'll find yourself easily accessing this new adventure upon its release this fall and getting into the action. But those unfamiliar with the series might want to play the original game first, though, as it's possible to get lost rather easily.

The main portion of Episode One's upgrading is to enhance the single-player experience, expanding on an already shuttered universe with a few twists in the storyline. However, Valve has indicated that a few of the touches from the single-player mode will have some kind of effect in multiplayer, so when you hop online against friends you can see what comes into play. Again, the company's keeping pretty tight-lipped about the project, but, come E3, we should be able to get more hands-on with the game and see what kind of dynamic changes the company has in mind for this series of expansions.

The original Half-Life is still a blazing PC experience, and Half-Life 2 followed it with an utter sense of care and delicacy, while still kicking all sorts of ass on the market. If these two are any indication of Valve's dedication to the brand, then we should be in for quite a surprise with Episode One when it releases later this year for the budget price of $20. We'll be back soon with more story details and hands-on soon enough.