The acting is pretty good thanks to Vernon Sewell’s choices, though the narrative itself feels rather uninspired. Robert Flemyng portrays a geneticist who has inexplicably brought into existence a creature that transforms daily; during daylight hours it appears as "Clare" (Wanda Bentham), an attractive and energetic young woman, but at night it becomes a blood-drinking entity with indiscriminate appetites. Fortunately, Peter Cushing ("Insp. Quennell") is available to unravel the mystery. The use of color photography diminishes any potential for darkness or suspense, and the special effects, limited as they are, depend too heavily on traditional lighting tricks that don't translate well onto film. Those who have a fear of moths might find this particularly unsettling; however, the story does pick up momentum as Cushing’s inquiries begin to yield results. Ultimately, I found it to be somewhat formulaic and not very imaginative.

Source on TMDB