Episode 2 is set to feature as many different environments as Half-Life 2 itself, with a missile silo and mine shaft heading up the list of locales. In the story department, Alyx Vance and Dr. Freeman are still on their way to deliver the mysterious combine packet. Apparently the next episode will also flesh out the equally-mysterious Vortigaunts, and even more perplexingly the G Man.
In addition, theres a Mad Max-style ramming vehicle, used in Episode 2 to charge through armies of new 'Mini Striders', first seen in the teaser trailer. A brand new weapon is also promised, the 'Strider Buster'. It will be used to target the Strider's new "weak spot" to a devastating effect. New functionality is also promised for the gravity gun, and a new yet-to-be-announced multiplayer game is set to ship alongside Episode 2. Half-Life 2: Episode 2 is planned for release this Christmas.
News Source: computerandvideogames.com