Some decent ideas, a genuinely suspenseful scene or two and a great performance from Margaret Johnston unfortunately aren't enough to elevate this beyond modestly entertaining retro cheese. A remake focusing more on the husband and wife's relationship and placing the supernatural mumbo-jumbo on the backburner could be pretty interesting.
Very tight script and effective direction make this one an entertaining and underrated chiller. Most of the horror remains either suggested or unseen, with the exception of the climax (maybe an inspiration for the blind pianist's death sequence from Dario Argento's Suspiria?) which is surprisingly well made. I enjoyed this more than the similarly themed Night of the Hunter actually. Wyngarde and Blair are wonderful.