I can't remember the name of it or the characters. I remember a couple lives across the way from an older woman who turns out to be a witch. She feeds the man herbal tea that over time mutates his soul so it resembles her body and no longer fits his own. Eventually he feels extremely broken down and she uses a kiss or mouth to mouth to swap their souls.

Familiar to anyone? I have been trying all sorts of search variations here and FM and striking out.

Thanks!!

Frank