“Made at the height of Italy's golden age of gothic horror, NIGHTMARE CASTLE has long been cherished by horror fans as perhaps the ultimate visual tribute to its leading lady / Italy's first real scream queen, Barbara Steele -- who had already captivated viewers with her sinister, uncanny beauty in films like BLACK SUNDAY and THE HORRIBLE DR. HICHCOCK.
The story is extremely gothic with a bit of E.C. Comics nastiness thrown in. We open with the final hours of the unhappy marriage between an aristocratic scientist (Jess Franco regular Paul Muller) and his raven-haired wife (Steele), who engages in secret trysts with the hunky handyman (peplum regular Rik Battaglia). When hubby catches them in the act, we get scenes that push the boundaries of kinkiness as far as '65 cinema would allow: he chains them to a wall, whips them, splashes some well-placed drops of acid, ties her to a bed, electrocutes them both in mid-embrace and slices out their hearts while charring the remains into potted plant ashes…” (Mondo Digital)