@fishscorpio, you are quite right. "William Wilson" is the third segment of Spirits of the Dead, with Brigitte also making an appearance. The first two segments are also based on Poe's short stories, "Toby Dammit" and "Metzengerstein". Katia is absolutely gorgeous-- I'd read about her nude scenes in The Lovemakers (1970) but have never been able to track down a copy.
@eGaTS, mea culpa, you are right it's Katia Christine but in the film "William Wilson" made after a short novel from Edgar Allan Poe. BB is also actress in this film