I10: Ravenloft II: The House on Gryphon Hill
I10: Ravenloft II: The House on Gryphon Hill is an adventure module for the 1st edition of Advanced Dungeons & Dragons. A direct sequel? Side-quel? Spinoff? to I6: Ravenloft, it revolves around the players trying to thwart the efforts of two evil beings; the vampire Strahd von Zarovich and the lich Azalin Rex, while the module also recommends you gaslight your players when appropriate about what is actually going on or if anything that happened in I6: Ravenloft was just a mass fever-dream.
following up if the party beat Strahd in the last adventure or was TPKed in the first module (the book even recommends Strahd kills the party even if they win) the players wake up from a fever, equipment scattered across town for "everyone's safety" in the town of Mordentshire with no memories how they got there except for receiving a request letter from a local church about Lord Byron Weathermay wanting the party to investigate his daughter's mysterious fiancé, an alchemist and sage, Count Strahd Von Zarovich... Dun Dun Dunnn.
Well... not exactly that Strahd, this one is a blond not vampire, and the couple is also suffering from the same delirium fever as the players and can't answer questions about why he ran from his House on Gryphon Hill, a now re-haunted house that was built 400 ago by Lord Wilfred Godefroy. At the end of the Gryphon Hill dungeon they only found that a massive machine in Strahd's lab was recently moved.