Moonmist is an interactive fiction computer game implemented by Stu Galley and published by Infocom in 1986. By using Infocom's portable Z-machine, the game was released simultaneously for many popular platforms, including the IBM PC, Apple II, Atari ST and Commodore 64. It is Infocom's twenty-second game.
The player's character is a young detective, asked by friend Tamara Lynd to investigate her new home of Tresyllian Castle in Cornwall, England. Tamara has recently become engaged to the castle's lord, Jack Tresyllian. She was very happy until she began seeing what appeared to be The White Lady, a ghost who has allegedly haunted the castle for centuries. As if seeing a ghost wasn't nerve-racking enough, she's also begun to fear for her life. Is Tamara's imagination just overly excited from living in a large old castle, or is someone really trying to kill her? And if her life is in danger, is it from a ghost or someone using it as a disguise?