Filmed on location at Castillo de Vinuelas outside of Madrid, Marisa Mell plays 'Marta', a woman who becomes the 'captive' of a wealthy, disturbed bachelor Don Miguel, played by Stephen Boyd, in his vast castle. We find out she is looking for her lost sister Pilar, who used to be Arturo's wife. Both actors do a great job in this film. Stephen Boyd gets to show off his acting chops as the disturbed yet charming Miquel. He is mostly placid and engaging, but the more he reveals about his life, the 'Norman Bates' side of his character starts to seep through. Marisa Mell holds her own vs Boyd as Marta, and the romance that happens with her and Miquel is the best part of the story. At the time, Marisa Mell and Stephen Boyd were real-life lovers, so the love scenes they have together on screen are genuinely electric and very sexy (with frequent Marisa Mell nudity!).