Left 4 Dead 2 is the sequel to the best-selling and critically acclaimed cooperative multiplayer smash from Valve, creators of "Half-Life," "Portal," "Team Fortress" and "Counter-Strike." Introducing melee weapons and new enemies to the original's award-winning gameplay, "L4D2" casts players as one of four new "Survivors" battling zombie hordes as they travel from Savannah, Ga., through New Orleans' French Quarter.