Half-Life spin-offs and expansions have met with varying degrees of success, from the meteoric (Counter-Strike) to the mediocre (Blue Shift), but they've all had one thing in common: None of them have been developed by the series creators at Valve Software.
That's set to change with the release of Half-Life 2: Aftermath, the first Valve-created expansion for the series. A new half-minute trailer centered around Alyx Vance confirms her prominent role in the game and should whet an appetite or two. Alyx's sidekick Dog, rumored to make a re-appearance in Aftermath, also rears his head in the trailer.
For more on the upcoming episode, check out GameSpot's recent interview with Valve programmer/designer Robin Walker.