An enchanting mixture of classical horror elements (B&W photography, Universal/Hammer atmosphere, a stage-driven, elegant quality) and early modern sensibilities (unpolite tension, unsafe scares, and the blind women-killing henchman of Morpho is a very memorable and scary character) that makes it much better than its French forebearer, Eyes Without a Face. And its eerie soundtrack is also one of its best elements.
Beginning of the friendship of Jess Franco and Howard Vernon and their love for handcuffed young women. This movie has a classical style with atmospheric shots and a Gothic style that is not present in Franco's later color films, but the plot rips-off "Eyes Without a Face". Terrible subplot where detectives go around stupidly don't help and neither do the sloppy shots of body doubles who show off their tits.