Knock Knock, a stealth horror game originally released on PC in 2013, will be coming to the PS4 on September 10.

Touting an unusual is-it-real-is-it-not backstory, developer Ice-Pick Lodge states that it developed the game from a strange email that arrived at the studio one day.

“What do you, a small-to-mid-sized indie studio, do when an e-mail pops up full of mysterious scribbles, notes, and audio files — coupled with a vague description of a possible game?” states a post on the PS Blog.

“In all honesty, more often than not you probably try to conjure up a polite and friendly response; perhaps discuss the sender’s ideas with them. But that’s not what happened at Ice-Pick Lodge studios in November 2011.”

Writer/Translator Alexandra Golubeva goes on to add that the quirky, hide-and-seek, cabin-in-the-woods story bases its central motif on the fear of the unknown.

“But that’s not all. Further to the Kickstarter and original release on PC in 2013, the “spooky sender” apparently contacted the studio again, claiming that while it had made mistakes, it got the “general gist just right.”

“We were — and still are — a bit afraid of what we’ve done, you see,” adds Golubeva. “Even those of us who were positive it was nothing more than a prank.”