A Valve employee reportedly revealed the existence of a "Left 4 Dead" sequel in a screenshot leak.

Valve's conceptual artist Tristan Reidford, the person who designed ATLAS and P-body from "Portal 2," has made a tutorial for Destinations Workshop Tools on the official Valve developer community site.

A folder named "left4dead3" is clearly seen on one of the screenshots. It was since taken down and replaced by an "obviously photoshopped" image, but the original one was already screencaptured and posted on the ValveTime forums.

The forum poster Smash speculated that this might be a deliberate tease from Reidford rather than some honest blunder.

"From the pessimist's perspective, this was just a mistake," the forum user wrote. "But it's too convenient that the folder viewport was scrolled exactly so that left4dead3 was shown first."

Gamespot reported, however, that there is a possibility that all employees at Valve have those folders on their computers, regardless if they are working on it or not. Although it is strange that Valve had to pull out the original image and replace it with a photoshopped one.

This is not the first time that rumors about "Left 4 Dead 3" has surfaced. In 2013, a "Left 4 Dead 3" listing was spotted in Valve's office by a touring group of Dota 2 redditors.

Another leaked was provided by ValveTime, this time providing screenshots of Valve's internal project tracking-software which showed a 68-person mailing group for a project titled "Left 4 Dead 3."

It has been almost four years since Valve confirmed that it had been working on a new game engine for quite a while, and is just waiting for the right game to use it for.

Fans are still waiting for other games from Valve, like "Half-Life 3" and "Portal 3." Valve's inability to release games with a number 3 on it gave birth to the internet meme "Valve Can't Count To 3."

"Left 4 Dead 2" was originally launched for PC and Xbox 360 in 2009, followed by a Mac port in 2010 and Linux port in 2013.