Valve announces Scavenge mode is the fourth game mode in Left 4 Dead 2, offering a couple of screenshots and details on how it will work. There are hands-on previews on G4tv.com and IGN, a Scavenge Victory gameplay video and a Scavenge Sword Gameplay Video on GameVideos (as well as a Jockey gameplay video), and here's word:

Oct 8, 2009 - Valve, creator of best-selling game franchises (such as Half-Life and Counter-Strike) and leading technologies (such as Steam and Source), today announced Scavenge, the fourth game mode to be included in its upcoming zombie thriller, Left 4 Dead 2.

Scavenge mode challenges players to compete in round-based games of up to 8 players (Survivors vs. Infected). The Survivors must battle both the Infected and the clock as they collect gas cans to refuel a generator located in each map. Every can the Survivors pour into the generator scores their team a point and adds time to the clock.

On defense, the Infected team plays as the boss Infected (including the new Spitter, Jockey, and Charger). They must keep the Survivors from fueling the generator by attacking them, destroying the gas cans, or running out the clock. During a round, each team gets an opportunity to play both sides, with the round going to whichever team successfully delivers the most cans.