Mystery House is an adventure computer game released in 1980 by Roberta and Ken Williams for the Apple II. The game is remembered as one of the first adventure games to feature computer graphics and the first game produced by On-Line Systems, the company which would evolve into Sierra On-Line. Because of its use of graphics, GamePro named Mystery House the 51st most important game of all time in 2007.
The game starts near an abandoned Victorian mansion. The player is soon locked inside the house with no other option than to explore. The mansion contains many interesting rooms and seven other people: Tom, a plumber, Sam, a mechanic, Sally, a seamstress, Dr. Green, A surgeon, Joe, a gravedigger, Bill, a butcher, and Daisy, a cook.
Initially, the player has to search the house in order to find a hidden cache of jewels. However, terrible events start happening and dead bodies (of the other people) begin appearing. It becomes obvious that there is a murderer on the loose in the house, and the player must discover who it is or become the next victim.