Today Valve announced that Left 4 Dead will be getting another batch of downloadable content this year. The "Crash Course" DLC will arrive on the Xbox 360 and PC in September.

"Crash Course" is a new cooperative campaign. It's said to bridge the gap between "No Mercy" and "Death Toll" campaigns, which is surprising because I had no idea these campaigns were actually a linked, linear story. "Crash Course" can be played in Versus and Survival modes as well.

It sounds like "Crash" will be shorter than average, as the press release mentions it will "deliver a complete Versus mode experience in just 30 minutes." The update will also tweak the game, adding a recharge timer for Infected teammates in Versus mode as well as reworking item spawn behavior.

The new DLC will be free of charge for PC gamers. Xbox 360 owners, however, will need to shell out 560 MS Points ($7).