One shot: The Pitt, infected

Even before the upcoming episode-linking Crash Course DLC was announced, Left 4 Dead fanatics were hard at work piecing together the game's deeper underlying story we were all too frantically struggling to survive to notice.

Unearthed: the game's location (Pennsylvania, notably No Mercy's Philadelphia and Dead Air's Pittsburgh, making it the second Wasteland of a city that year), the map that draws a solid line between each episode (above), and screenshots and dialogue of the half-infected news-chopper pilot who we presumably will see more of in Crash Course proper. [via Tom]