Though it was originally thought to be a Left 4 Dead prequel, it turns out that Overkill's Payday: No Mercy is actually just set in L4D's Mercy Hospital, and is non-canonical for Valve's L4D universe. Still, that's not to say the game won't be a lot of fun. After the jump, check out a new trailer.
Valve's Chet Faliszek told Kotaku that "This is a 100% Overkill made mission for Payday: Heist simply set in No Mercy hospital from the Left 4 Dead series. It is not telling the origins of the Infection and is not canon. There is a little cameo from one of the L4D characters (the comic should give you a hint) and a fun little easter egg with a payoff later in Left 4 Dead. Just us having some fun with a studio we are friends with and who have also made a great co-op game."