[Update: The official YouTube video was taken down, but IGN managed to snag it before it was hidden.]
I've been looking forward to seeing how the whole Payday: The Heist and Left 4 Dead crossover was going to happen. Today, we're treated to the debut trailer which shows the clown-faced criminals of Payday in Left 4 Dead's No Mercy hospital.
The Payday criminals are at the hospital on a mission to retrieve some blood from a patient in quarantine. Is this perhaps patient zero, and is this what unleashes the whole outbreak in the first place? The YouTube description asks "Have you ever wondered how the Left 4 Dead series began?" Followed by, "It started with a heist!"
As far as crossovers go, this is looking really awesome.