Details about the Valve and Overkill Software team up have been revealed today; it is a DLC pack for Payday: the Heist called No Mercy. Unfortunately, Valve has debunked the rumour that the DLC would be a prequel to Left 4 Dead. However, the content will still be a cross over between Left 4 Dead and Payday: The Heist. It will apparently be a single piece of DLC for Payday: The Heist that will take place inside Left 4 Dead's "Mercy Hospital." A trailer for the game was posted earlier today, with the beginning of it showing the phrase: "Have you ever wondered how the Left 4 Dead series began? It started with a heist,". However, the trailer was quickly pulled down and a new trailer was put up without that phrase in it, because according to Valve the mission description resulted from "over-excited marketing guys." Valve has confirmed that this DLC will not be considered cannon from the Left 4 Dead series, basically it is a piece of DLC that takes place inside the world of Left 4 Dead. There will be a cameo of at least one Left 4 Dead character in No Mercy, but we don't know who that character is right now. Here is the official statement from Valve:
"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."No official release date for Payday: The Heist No Mercy has been set at this time. Hopefully we will have more details in the near future.