PAYDAY: The Heist devs Overkill Entertainment and the Left 4 Dead team over at Valve are working on an “in-depth collaboration” together.

“As perceptive gamers will have noticed, several hints have recently been dropped into Payday The Heist, which has led to various rumors,” said Overkill studio game director Ulf Andersson.

“We are excited to be able to confirm that an in-depth collaboration between Overkill and Valve is currently in production.”

“We are working on a very cool blend of PAYDAY and Left 4 Dead. I am sure it is so exciting that it will have some players check into the hospital before we are done.”

Just what they have in store is anyone’s guess. I wonder if we will see something at E3?