There are a couple of mystery games that are available in early access/beta that already use LLM AI to generate dialogue.

I’ve messed with 1 and it’s alright. The problem with it is mostly in how it doesn’t necessarily regurgitate the info it knows into something coherent and logical to actually solve the mystery. That or they never ever tell you the truth. Since the only way to solve the mystery is by talking to NPCs, it often leads to unsolveable mysteries.