Sleuth About Town
I can fill in on that - every mystery has between 5 and 12 suspects. A beginner's mystery will start with 5 and will grow directly proportional with the level of difficulty. Consulting the fates at the Fortune Teller will yield one of three possible results:
'You have only just begun...' meaning you need to find at least three more suspects.
'You have already passed many signposts...' meaning you need to find up to two more suspects.
'...all the actors have taken the stage...' which, of course, means that you have found all the suspects.