Not sure if this is the right place for something like this, but I'm writing a game for my D&D group next month. The gist is that there's a ghost haunting a wizarding school and our group is being asked to figure out what it wants, since it won't talk to any of the professors.

The first third is going to be roleplay heavy -- they have their entrance interview (complete with false identities), then have to work out how to get themselves detention and deal with some bullies without outing themselves or getting actually arrested.

The final third is going to be combat heavy -- they discover the murderer and subdue (or more likely kill ... le sigh) him, then deal with a group from the organization he's working with.

But I'm stuck in the middle third, which I want to be more puzzle/investigation type stuff. Usually this is the stuff I love making, but for some reason with this game it's just not happening. Part 1 ends with them finding the ghost's corpse, locked away in a room no one has really entered since she died in it. There's information in that room showing she was developing a new spell, and also that she worried someone at the school was going to steal and sell her new spell for their own profit.

I need to get them from the murder room to the teacher who actually did the murder (and who totally did end up stealing and selling the spell too). My initial thought was to have only one person who was at the school during the murder and also in present, but that feels way too boring. Then I thought they could trace back this spell to whoever sold it initially, but that would be a lot of travel for the group and would likely blow their cover. And now when I try to think of other ways to get them to this guy, my brain just goes "no, use the timeline thing, it's easy and that's fine."

So I come to you creative folks to see if anyone has any ideas to break me out of this rut. The group is fairly high level (8-9) and includes a wizard, warlock, paladin and rogue, so things that require more advanced abilities are fine. Any help would be endlessly appreciated.