Hammer Films question
When I was a kid TBS or TNT had various Hammer films running in the afternoons. I found this one, and a few others, but there is one that has been bothering me - I can't figure out the title or if it's even a Hammer film.
The plot is (as I recall) about a guy (in modern time) who falls in love with a girl, who has a sister who got burned at the stake centuries ago during the witch trials, but instead of letting her sister die, the lead girl gives her soul and her faith to the devil to save the sister. The sister was horribly disfigured and looked really old in modern time (and didn't speak much, just looked mysterious and spooky) but the lead female was still youthful and pretty. I guess at the end, the guy had to save the lead female because she was aging quickly, and he ended up giving HIS soul to the devil to have her young again. Does this ring any bells with anyone? It was made in the seventies. I think the lead girl aging quickly had something to do with either the sister dying, or the guy loving her. I remember she didn't want him to make the same decision she had made.