This is a single player puzzle map that Requires Headphones and the Game mode Nightmare Mode.
(Please Note that Our Nightmare 1 and 2 cannot be played with Nightmare Mode)
This is the 3rd map in the series, however the first 2 aren't that great in my opinion.
I cannot really explain the map with further detail than to wear headphones, maybe turn off the lights and make sure you're playing solo. It also helps to not have anyone in party chat.
This is a puzzle map. A Horror Nightmare that never ends.
I don't want to give it all away.