
No other details are available right now, but it's safe to say that Episode One/Aftermath (whatever you wish to call it) will not be answering all of the questions left open by the Half-Life 2 ending. According to CVG, who will soon post an interview with Episode One designer Robin Walker, the initial release will offer around 5 hours of gameplay and will give more details as to the G-Man's involvement and the fates of the Breen and the Citadels.
[Thanks, Jon D and the "almighty" Ludwig]
