I'm looking for a fic that has the base from the movie "Haunting" I believe.
Chris was conned by Mary (she's evil in this or a possesed by the house) to host a supernatural evening on a house he owns. The Larabee mansion has been haunted for ages and has taken the lives of many Larabee men through the years. Mary invites a whole host of scientists to prove the house is haunted as well as people who claim to be psychic or just have powers, a kind of scientists versus supernatural types.
All of the seven are there plus Cassie, Nettie and Mary and a bunch of college kids and a professor. Vin is a powerful psychic that lives with Nettie and has locked in himself because of past abuse.
The house locks them in and kills a buch of people and it needs Vin to complete a ritual or something to the effect. Under the horror story is the story of the Magnificent Seven that lived in the old west and their story is linked with what's happening.
The ending is rather marvelous when they escape the house and Chris realizes that Vin is his missing kid brother that he'd thought had died when they were children. He didn't realize because the abuse Vin suffered destroyed Vin's hands (he was called a elf because he had six fingers in his hands and those had to be cut off due to damage).
A very long fic and I adored it to pieces, I read it awhile back when I was going through a Magnificent Seven binge and apparently didn't remember to bookmark, idiot me.
Thanks a million in advance to the lovely soul that finds it. I haven't a clue who wrote it or even where I read it. If you need more info on the fic just poke me and I'll provide if this doesn't jog anyone's memory.
FOUND! by the wonderful etakyma. It is Retirw's "Petrie's Folly."