Daughter of Darkness was based on They Walk Alone, a play by Max Catto. The heroine of the play can be described as a "homicidal nymphomaniac," which understandably posed censorship problems when the Catto original was adapted to the screen. In her second film, Irish stage star Siobhan McKenna plays Emma Baudine, a "black widow" who lures men with her sexual charms and then murders them. Because she is the trusted assistant of village priest Father Corcoran (Liam Redmond), no one suspects what Emma is up to -- no one, that is, except the inquisitive Bess Stanforth (Anne Crawford), who emerges as the heroine of the piece. Also appearing in her first movie role is Honor Blackman, long before her international TV fame vis-a-vis The Avengers.
by Hal Erickson synopsis