Article.
Summary of the article:
-Valve produced, in house, a 4 issue miniseries of comics as a prequel to The Sacrifice. You can read them here. (As of this posting, only the first 4 were released.)
-This features the original 4.
-This further links the original 4 and the southern 4. Essentially, expanding and joining their stories.
-One of the original 4 will die.
We've seen prequel comics for games before (Dead Space is one) and comics that continue a game franchise's story (Halo, WoW, etc.), but they're typically not free. They are usually the cost of a standard comic, or if online for free, much smaller. So it's cool to see a "big publisher" go this route.
It's also cool that they're not only going back to the original characters, but the release is for both games.
If you have Steam, I recommend checking out the trailer. It doesn't have any sound, just some music. I think it works for the story.
While we're talking about this, one area I think Valve and Steam suck is delivering non-game software content. They need to improve their news section to let people know about events like this one. I shouldn't be finding out about it via a third party site, particularly when I'm logged into Steam most days of the week.