Valve has shown off the promised Swamp Fever campaign at Comic-Con in San Diego, revealing new infected types along the way.
There are several to go through, including a new special infected, the Spitter. Her flobby oral output is like napalm, crawling over the ground and splitting players up, or causing sustained damage if it touches anyone.
Then there are a couple of new "uncommon common" infected, including riot cops who can only be taken down from the rear, thanks to their Kevlar coating, and the mud men, who crawl along on all fours - particularly unhelpful when you're waist-deep in swamp water that covers their approach, by the sound of it.
Speaking of the water, you'll want to avoid it as it slows you down, but staying on solid ground will be tricky, and there are other environmental implications too. The Hunter, for example, can pounce from underwater...
Previews coming out of Comic-Con mention new gauntlet moments too - these are Left 4 Dead 2's new equivalents to the end-of-level sieges, and play out as breakneck headlong charges through swarming infected and perilous terrain. Swamp Fever apparently has a tussle on and around a crashed plane and another involving a ferry. The first campaign we were shown, The Parish, had you racing along a bridge.
You can read about how that played out fully in our Left 4 Dead 2 hands-on preview. You should also check out our Left 4 Dead 2 EGTV Show while you're at it. Look out for our own Comic-Con impressions soon.
Left 4 Dead 2 is due out for PC and Xbox 360 on 17th November.