Not content with unleashing a full-blown zombie apocalypse, Valve has come up with the second most socially awkward event imaginable: inviting characters from the original Left 4 Dead to hang out in the sequel's first DLC campaign. Bill, Louis, Zoey and Francis will meet with the stars of Left 4 Dead 2 in "The Passing," which Valve VP of marketing Doug Lombardi calls "the most important campaign in the Left 4 Dead story, as all the Survivors are being called together in one campaign." It's targeted for release in early 2010 on Xbox 360 and PC. In addition to a co-op campaign (set in rural Georgia) and a new "co-operative challenge mode of play," The Passing will offer new content for Survival, Versus and Scavenge modes. Playing as the L4D2 cast, you can also expect to encounter a new melee weapon, firearm and "uncommon common" zombie. We can't wait to meet up with last year's survivors again ... oh, assuming they really are still survivors.