As far as Valve are concerned, you're still playing Half-Life 2, and if Gordon Freeman hasn't been anywhere since his last outing, then why the hell should you? No, for very much better and (as we'll see later on) a little worse, this is a direct continuation of that game we knew and loved all of 18 months ago.
It won't break the habit of a lifetime by explaining its intricate plot in its first scene, nor will it magic up a new setting for the sake of it, or invent all manner of new power-weapons that the Combine must have forgotten about the first time around. It isn't a new game, nor is it an expansion in the traditional sense. Don't expect Episode One to be something it's not.
