Valve has announced that it will be releasing new downloadable content for Left 4 Dead titled “Crash Course”. The content will add new single-player, multiplayer and co-op gameplay and is targeted for a September release date.

The new “Crash Course” chapter will “[bridge] the gap between the end of the “No Mercy” campaign and the beginning of “Death Toll” in the original game, expanding the game universe with new locations, new dialogue from the original cast, and an explosive finale,” Valve promised in a press release.

“Since the release of Left 4 Dead last November, the design team has been excited about creating new experiences for this world and allowing players to do the same, by releasing much of our internal toolset, like the Survival Pack and Authoring Tools,” said Gabe Newell, managing director of game development at Valve. “We’re working with the fans toward the ongoing entertainment value of the product.”

Crash Course will be free on the PC, while Xbox 360 owners will have to pay $7, or 560 Microsoft Points.