A creature that has climbed aboard the ship seems somehow familiar. Discard 1 defeated investigator token from the game board, then a Deep One Monster ambushes you! If you defeat it, the fate of your colleague haunts you; lose 1 Sanity and gain this Clue. If you do not defeat it, advance Doom by 1.
What exactly is supposed to happen if there are no defeated investigators on the board at the time of this encounter? While the effect does not specify that you have to discard the token for the rest of the text to occur, it makes no sense thematically to handle it otherwise.