There are a few games linked at this site that were inspired by the board-game Clue. I've been unable to figure out precisely which of them can and which of them can't be played as one single player. From their descriptions they sound like they can't, although some mention 1-6 players as a possibility. I'm not sure that it's not a mistake, though, and they're large
So I thought maybe uploader or somebody else who played them knows which can be played as one player, without friends, for sure?
Here are the titles:
Clue (1996)
Clue Chronicles: Fatal Illusion (2000)
Clue Jr.: SpyGlass Mysteries (1999)
Clue: Master Detective (1989)
Clue: Murder At Boddy Mansion (1998)
Foul Play: Mystery at Awkward Manor (1995) (the links are down)