I'm assuming you joined the Fabulous Five. If so you may want to
speak to the mayor


Also depending on where you are in the murder mystery and what you have done you will find more info about it. I'd ask you to screenshot your quest log with the quest open and I'll see what might be missing if that will help.

I like that the game isn't super hand holding with it's quests. Yes, at times it can be annoying, but I like that I have to hunt to figure out the rest of the quest line.