Poltergeist: The Legacy - Season 4 Episode 19 Sabbath's End
Overview: Kat faces mortal danger when she resumes her friendship with an ailing Miranda. To save Kat, Rachel must find powers from the past, a past she would prefer to forget. For this episode, we learn that Miranda wants to transform herself into Kat - to inhabit Kats body. To live in Kats body. After the opening credits, Kat and Rachel have an argument and Derek tries to persuade Kat to give up magic - she disobeys, obviously. After a ritual between Miranda and Kat, Miranda tricks Kat and Miranda transfers her soul into Kats body - but before she does, Miranda reveals her true self - elderly, dying old women who has been searching for the perfect body to transfer into. Miranda is now in control of Kat.
Comment
I'd say it was unique, but Friday the 13th had an equally good series like this based around an antique shop. And, of course, it is like the X-Files and Warehouse 13 and Mellinum...but there are reasons that shows like this are made and develop a cult following. They are almost always really good. I think the draw back to the show is that it has the title "Poltergeist" and like "Friday the 13th" that kind of set people up for a let down when they realized that it had little to do with the movie franchise. But, if you accept that it's not based around the film franchise, you can sit down and experience a very entertaining horror show that should have been far more popular.