Peter De Mendelssohn's novel Marianne of My Youth was the source for this mystical romantic drama. Marianne (Marianne Hold) is the Bavarian sweetheart of wealthy young Argentinian finishing-school student Vincent (Pierre Vaneck). Hero meets heroine when his schoolmates lock him in a crumbling mansion as part of a fraternity initation. The ethereal Marianne insist that she's the prisoner of the ogre of the castle--her ageing, debauched lover. An idyllic romance follows. . .but is Marianne all that she claims to be? Can it be that Marianne is merely a figment of Vincent's youthful imagination?
Source : allmovie.com