The upcoming No Mercy map for Payday: The Heist, has been described as something of a prequel to Left 4 Dead, but Valve has now set the record straight.
"This is a 100 per cent Overkill made mission for Payday: The Heist simply set in No Mercy hospital from the Left 4 Dead series," Valve's Chet Faliszek tells Kotaku.
Valve revealed the it's more of a casual link between the two developers:
"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."
The Youtube video released for the new map (now removed) had Overkill describing the map as follows:
"Have you ever wondered how the Left 4 Dead series began? It started with a heist!"