You play a young American detective who has been summoned by your friend Tamara Lynd to her new home in Cornwall, Tresyllian Castle. Tamara has recently become engaged to the castle's lord, Jack. Sometime afterward, she began seeing the White Lady, a ghost who is said to haunt the castle, as well as experiencing attempts on her life. And so, she has called you in to investigate.
Contains examples of:
- Difficulty Levels: Early in the game, the player is asked their favorite color, and the answer determines which of four different mysteries (differing in complexity, and each with a different guilty party and a different reward) the game subsequently presents to the player. The options in order of ascending difficulty are green, blue, red, or yellow.
- Faking the Dead: In the red variation of Moonmist, we discover that Lord Jack Tresyllian attempted to kill his former fiancée, Deirdre Hallam, after murdering his uncle Lionel for his inheritance and fortune. However, she escaped Jack's clutches by jumping into the well in the castle basement and swimming her way to safety, thus faking her own murder and setting the one reason for "Never Found the Body"; she then masqueraded as the legendary "White Lady" in her effort to haunt Jack and her successor Tamara Lynd.
- Foreign Remake: In 1992, six years after the original Moonmist, Japanese software development company SystemSoft developed and published its remake for the PC-9801 entitled Moonmist: Shiroki Kifujin no Nazo (ムーンミスト ～白き貴夫人の謎～; Moonmist: The Mystery of the Noble White Lady). Unlike the original, this game has some of the most common verb commands ("look", "take", etc.) that can be accessed by pressing a corresponding button (the player still has to type the name of an object, though), and enchanced graphics for the unique background pictures on which the text is super-imposed.
- Hello, [Insert Name Here]: The game asks you for your name and title at the beginning.
- Never Found the Body: We are told that Deirdre Hallam apparently died when she allegedly jumped or fell into a deep well at the basement of Tresyllian Castle, and her body was never found, although it is later revealed in the red variation that she was actually Faking the Dead.
- One-Word Title
- Purely Aesthetic Gender: A bit of a difference depending on which version of Moonmist you've played: while the original game only has you customize your character in the forms of Hello, [Insert Name Here] and Schrödinger's Gun, the PC-9801 version not only ditched the prefix in place of this "Purely Aesthetic Gender" (with an option of either male, female or "okama", i.e., Drag Queen), but it also allowed you to type in the number of your age.
- The gender you pick does effect some interactions with supporting characters Iris Vane and Ian Fordyce, who will show some slight romantic interest in you (and can even be kissed) depending on your selected gender. Lord Jack as well has a notable reaction upon meeting you if you're playing as a female in the red version.
- You can as well choose a gender-neutral prefix, or a foreign language or nonsensical one, and the game will treat you as gender-non-specific.
- Schrödinger's Question: You are asked your favorite color at the beginning of the game. Your response determines the identity of the "ghost." (Adaptive puzzles are a common feature of IF games.)
- The book on ghosts included in the Feelies has a sticker indicating it was checked out from the town library of Festerton, where fellow Infocom game Wishbringer takes place.
- In the yellow variation of Moonmist, three of the four clues you are sent to find are references to the works of Edgar Allan Poe, namely, "The Bells", "Annabel Lee", and "The Cask of Amontillado".
- Title Drop: The hidden treasure of the green variation is a rare South American tribal remedy by that name. It doesn't factor into any of the other versions at all though.