Knock Knock actually began as as random email received by the developer studio Ice-Pick Lodge to create a game based on bits of text, audio, and some video footage. Taking on the challenge, the end result became Knock Knock.
What is Knock Knock all about? In a wooden house, a single man lives by himself. The house receives visits from unusual guests that knock on the window to ask the old man to play a game of hide-and-seek. To win, the old man must stay alive and maintain his sanity until sunrise. During this time, more visitors are on their way, and are coming for the old man. The player must repair the gaps and breeches in the house to prevent them from coming in, as well as finding items to aid in avoiding the monsters.
Additional details about Knock Knock gleaned from their home site:
Fill in the gaps. The house aids the Lodger, but must be repaired and maintained.
Seek. The Lodger lost something very important. The reason for what is happening is somewhere inside. Everything can be explained, you need only find the key and bring it to light.
Wait. In this game, you must watch and listen carefully. Inspect and scrutinize everything. You only need to last until sunrise.
Follow the rules of the game! Of course, as you play the game, the game also plays you.
It appears that Knock Knock isn't for those faint of heart, or bad at the game of hide-and-seek.