Valve hasn't had much of an issue infecting gamers with its newest survival horror shooter Left 4 Dead 2. Earlier this month, the studio announced that its frenetic co-op centric shooter had sold 2 million units at retail, a figure that did not include Steam sales. The NPD Group affirmed Left 4 Dead 2's fast-selling pace last week, saying that the game finished fifth on its November sales chart with 744,000 units sold in the US on the Xbox 360 alone.
Today, Valve announced that the game's growing horde will soon benefit from Left 4 Dead 2's first round of downloadable content. Titled The Passing, the add-on introduces new single-player and multiplayer content and is due for release on the Xbox 360 and PC in early 2010.
The Passing scenario takes places just after the Dead Center campaign. It ties together Left 4 Dead 2 and its predecessor from 2008, as it sees the original game's cast meeting up with the second game's contingent of survivors. According to Valve, The Passing DLC will be "the most important campaign in the Left 4 Dead story." The add-on will also introduce a new zombie type, melee weapon, and firearm.
Valve plans to announce pricing information closer to the pack's launch. The studio has been across the board with pricing for Left 4 Dead DLC. In April, Valve released its first Left 4 Dead add-on, the Survival Pack, for free for both the PC and 360. However, the second pack, Crash Course, carried a $7 premium on the Xbox 360 while the PC edition remained free.