Mystery House is anadventure game released byOn-Line Systems in1980. It was designed, written and illustrated byRoberta Williams, and programmed byKen Williams for theApple II.^[1]Mystery House is the firstgraphical adventure game and the first game produced by On-Line Systems, the company which would evolve into Sierra On-Line.^[2] It is one of the earliesthorror video games.^[3]

Mystery House
1982 re-release cover art
Developer(s)	On-Line Systems
Publisher(s)	On-Line Systems
Designer(s)	Roberta Williams
Programmer(s)	Ken Williams
Series	Hi-Res Adventures
Engine	ADL
Platform(s)	Apple II
Release	May 5, 1980
Genre(s)	Adventure
Mode(s)	Single-player

The game starts near an abandonedVictorian 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, aseamstress; Dr. Green, a surgeon; Joe, a grave-digger; Bill, a butcher; Daisy, a cook.

Initially, the player has to search the house in order to find a hidden cache of jewels. Soon, dead bodies (of the other people) begin appearing and it is obvious there is a murderer on the loose in the house. The player must discover who it is or become the next victim.

At the end of the 1970s, Ken Williams sought to set up a company for enterprise software for the market-dominating Apple II computer. One day, he took ateletype terminal to his house to work on the development of an accounting program. Looking through a catalog, he found a game calledColossal Cave Adventure. He bought the game and introduced it to his wife, Roberta, and they both played through it. They began to search for something similar but found the market underdeveloped. Roberta decided that she could write her own, and conceived of the plot forMystery House, taking inspiration fromAgatha Christie's novelAnd Then There Were None.^[4][5] She was also inspired by the board gameClue, which helped to break her out from a linear structure to the game.^[6]

Recognizing that though she knew some programming, she needed someone else to code the game, she convinced her husband to help her. Ken agreed and borrowed his brother'sApple II computer to write the game on. Ken suggested that adding graphical scenes to the otherwise text-based game would make it more interesting for players, and the couple bought a VersaWriter machine, on which users can trace over a line drawing and convert it to a digital drawing. Roberta drew seventy scenes for the game. Ken found, however, that the resulting digital drawings were too large to fit into a 5¼-inchfloppy disk, so he devised a way to convert the images into coordinates and instructions for the program to redraw the lines of the scenes rather than static images, as well as writing a better version of the VersaWriter scanning software. The resulting game is a text-based adventure with a depiction of the character's location displayed above the text. The game's code was completed in only a few days, and was finished on May 5, 1980. The couple took out an advertisement inMicro magazine as On-Line Systems, and mass-producedZiploc bags containing a floppy disk and a sheet of instructions, to be sold atUS$24.95 (equivalent to $95.22 in 2024).^[4][7]

To the Williamses' surprise, what Roberta had initially considered a hobby project sold more than 10,000 copies through mail-order.^[8][4][9] Including its 1982 rerelease through the SierraVenture line, 80,000 units were eventually sold worldwide,^[10] making it one of thebest-selling computer games at the time.^{[citation needed]}

Mark Marlow reviewedMission: Asteroid,Mystery House, andThe Wizard and the Princess forComputer Gaming World, and stated that "Mystery House is considerably more difficult and provides many traps for the unwary in a wonderfully Victorian setting".^[11]

Computer Gaming World in 1996 ranked it fourth on the magazine's list of the most innovative computer games.^[12]GamePro namedMystery House the 51st most important game of all time in 2007, for introducing a visual component to adventure games and for featuring graphics at a time when mostcomputer games did not.^[13] Though the game is often considered the first adventure game to use graphics,dungeon crawlrole-playing video games such aspedit5 (1975) had already been using graphics prior to its release. Applying graphics to an adventure game, however, was unprecedented as previous story-based adventure games were entirelytext-based.

Mystery House's success led the Williams to create theHi-Res Adventures series, and note the game asHi-Res Adventure #1. After the follow-on success of their next game,Wizard and the Princess, the pair moved into game development full-time, and On-Line Systems was incorporated in 1980 as Sierra On-Line.^[4] The game was later released into thepublic domain in 1987 as part of Sierra's seventh anniversary celebration.^[14][15]

In Japan, several differentadventure games under the titleMystery House were released. In 1982,MicroCabin releasedMystery House, which was unrelated to (but inspired by) the On-Line Systems game of the same name. The following year, the Japanese company Starcraft released anenhanced remake of On-Line Systems'Mystery House with more realistic art work anddepiction of blood, for theNEC PC-6001 andPC-8801, whileMystery House II for theMSX was released as a sequel to MicroCabin'sMystery House.^[16] The Japanese versions ofMystery House had sales of 50,000 units, including 30,000 copies on theMSX and 20,000 copies on the PC-6001, PC-8001,PC-8801,PC-9801,FM-7, andX1 computers.^[17]

Mystery House was satirized in the 1982 adventure gamePrisoner 2. One location from that game is a spooky house, where the player is told, "He's killed Ken!" and must seek absolution for murder. Elements from the game were later reintroduced in the Sierra On-Line gameThe Colonel's Bequest in 1989.

• Mystery House atMobyGames
• Mystery House in theInteractive Fiction Database