Cacturne and Sableye i feel know something important. And i somehow feel a dark type would more than likely be one, being super effective to ghost (Exorcist joke haha)

I'll probably interview 41 Sharly the Whimsicott.

Solace Plaza seems a good place to investigate as well, as is Kinny's Tavern and The Platinum Tower. Just hunches i have, especially Solace which is what i'll most likely hit in the next Night Cycle.