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 grave-digger; 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 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.
Development and release
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 a teletype terminal to his house to work on the development of an accounting program. Looking through a catalogue, he found a game called Colossal Cave Adventure; after buying the game, he introduced it to his wife, Roberta, and they both played through it. Having finished Colossal Cave Adventure, 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 for Mystery House, taking inspiration from Agatha Christie's novel And Then There Were None. Recognizing that while 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's Apple II computer to write the game on. Roberta suggested that adding graphical scenes to the otherwise text-based game would make it more interesting for players, and the pair bought a VersaWriter machine, which allowed users to 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-inch floppy disk, and stored the images into the game as 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 was 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 pair took out an advertisement in Micro magazine as On-Line Systems, and mass-produced Ziploc bags containing a floppy disk and a sheet of instructions, to be sold at $24.95.
Reception and legacy
To the Williams' surprise, what Roberta had initially considered a hobby project sold over 10,000 copies through mail-order. Including its 1982 rerelease through the SierraVenture line, the game sold 80,000 units world-wide, making it one of the best-selling computer games at the time. Mark Marlow reviewed Mission: Asteroid, Mystery House, and The Wizard and the Princess for Computer Gaming World, and stated that "Mystery House is considerably more difficult and provides many traps for the unwary in a wonderfully Victorian setting." Computer Gaming World in 1996 ranked it fourth on the magazine's list of the most innovative computer games. GamePro named Mystery 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 most computer games did not. Though the game is often considered the first adventure game to use graphics, dungeon crawlrole-playing video games 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 entirely text-based. Mystery Houses success led the Williams to create the Hi-Res Adventures brand, and note the game as Hi-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. The game was later released into the public domain in 1987 as part of Sierra's seventh anniversary celebration. In Japan, several different adventure games under the title Mystery House were released. In 1982, MicroCabin released Mystery House, which was unrelated to the On-Line Systems game of the same name. The following year, the Japanese company Starcraft released an enhanced remake of On-Line Systems' Mystery House with more realistic art work and depiction of blood, for the NEC PC-6001 and PC-8801, while Mystery House II for the MSX was released as a sequel to MicroCabin's Mystery House. The Japanese versions of Mystery House sold 50,000 units, including 30,000 copies on the MSX and 20,000 copies on the PC-6001, PC-8001, PC-8801, PC-9801, FM-7 and X1 computers. Mystery House was satirized in the 1982 adventure game Prisoner 2. One location from the game was a spooky house, whereupon his arrival the player is told, "He's killed Ken!"—that is Ken Williams—and must seek absolution for murder. Elements from the game were later reintroduced in the Sierra On-Line game The Colonel's Bequest in 1989.
