There are times that something is brought up and then forgotten about. Ghosts season 5 is set to remind us of something that has likely been overlooked for some time.
Hetty knows a lot about her house, which isn’t that surprising considering she lived in it since she was a baby. Well, there are items that she owned that are still in the house, including a particular mummy. That mummy is about to come up in an exciting vengeful way.

Sam and Jay need to deal with a vengeful spirit in Ghosts season 5
Sam and Jay may want to call in the Winchester brothers in Ghosts season 5 if TVLine's tease is anything to judge. The two are about to get a visit from a vengeful spirit, and they don’t know all the tricks to hold them back!
That vengeful spirit will come up during the Halloween episode, which is also a moment for Isaac to face a huge lie that he’s told. As Nigel focuses on a séance to bring back Chris, Sam and Jay will need to deal with the ghost of the mummy.
All we know right now is that the mummy belongs to an Ancient Egyptian, who is angry that he has been brought to Woodstone Manor, and you can’t really blame him. He’s been taken from the resting place he thought he would have for eternity. I’d be angry as well!
So, he’s back for revenge against those who brought him to Woodstone, which means the Woodstones themselves, according to co-showrunner Joe Port. This could mean going after Hetty, as she’s the one who “owned” his remains, but it could also mean Sam, since she is currently the last surviving member of this family, even without the Woodstone name.
"We meet the ghost that inhabits that mummy. He’s an ancient Egyptian fellow, and he has an axe to grind against the people who brought his mummy here, namely the Woodstones.”

It’s time for more details about the mummy
Of course, as a lot of mysteries about the Main 8 ghosts have been solved, the show needs to delve into other mysteries. Halloween is going to be the perfect time for that in Ghosts season 5, especially with the mummy story.
Why hasn’t the ghost shown up in the past? That’s surely something that needs to be explained, and it’s likely to come from the fact that Sam and Jay are about to learn the gory details of the previously unknown resident.
Could we learn how he died? I’d settle for just who he was when he was alive, and why he hasn’t wandered the halls. Oh, and maybe his ghost power? I’m sure that’s to come up with the talk of vengeance.
Ghosts season 5 premieres on Thursday, Oct. 16 at 8:30/7:30c on CBS.