We never thought we'd have to slap a spoiler warning on a post about downloadable content for the Left 4 Dead franchise -- and yet, here we are. The latest episode of GameTrailers TV revealed an intriguing plot point about the pair of new chapters for the original game and sequel. We respect that some of you might want to remain in the dark about the DLC until you finally get your hands on it. For the rest of you, check out the details just past the jump.