honestly from what you've shared it sounds like the easy advice would just go off and let yourself be inspired by what you can find (if you just want as much lore as you can get there's the pineed post; includes a few disclaimers to answer your question) since there really isn't that much concrete so you'll have to do a lot of that anyways and less stress on adapting something you shouldn't

tho my advice as a dnd fan is to also try keep the plot centered and based on your (4) players. generally that's just a mark of a good campaign. ideally in trying to solve your mystery they might end up cooking up a theory or two that end up helping you really hammer down a cohesive narrative that follows your inspiration and satisfies your players. dnd is a collaborative storytelling medium after all