The series finale:
I thought maybe a Jack-the-Ripper type story--a serial killer of Collinsport's past comes back as a ghost and starts killing.
Regarding the living Mummy--suppose this was someone (lets give him a name: Ptah-hotep) with an unsual motivation? He's not looking for a lost love or revenge against a Collins nor trying to escape an enemy. Rather, he is looking for a way to die? He already made himself immortal and wants to end it, but can only die under some very specific circumstances--for example, if he can destroy his coptic jars, and he has reason to believe the last one is hidden somewhere at Collinwood?