I'd kind of like to have one of the characters be the killer, maybe. It would certainly make for an interesting game. Actually, it would be even better if there were more than one and we had multiple parties like [@ArenaSnow] suggested. 
Not sure if I can manage a DnD type setting exactly, but maybe I'll see if any ideas from that could work well with it. 

What kind of place would work best for this? I don't want it to be too small a place, but investigations would be easier on some kind of closed circuit, I think. It doesn't even have to be the same one for the whole game, but we'll have to see how one round goes first.