I am a huge fan of mysteries and I think this sounds super fun! I actually love the idea of it being part of an ongoing adventure mode gameplay option. After the initial event I think you should be able to find clues around the town and learn things thru interacting with sims. I wrote about this on another page, but it seems appropriate to add here as well- what if each town had it’s own mystery to solve. You could opt in to multiple challenges/missions to help uncover each town’s mystery. Collect objects, take photos, add notes and pictures to your notebook, receive letters/text/email clues, talk to NPCs that help direct you towards next steps or offer further insight...