It's striking how glamorous Lucille Ball appears at times within this skillfully assembled mystery, which notably lacks any genuine criminal activity. She’s brought into Scotland Yard to help them look into the disappearances of eight girls spanning recent years, one of whom is her friend. A shared element among these puzzling cases seems to be that each girl received a poem before vanishing, and they might have all answered a personal ad in the newspaper. Consequently, “Sandra” must reply to each advertisement hoping to catch whoever is abducting or harming these women (George Zucco delivers a strong performance as her police escort throughout this process). This portion of the film proves to be the most entertaining, as she meets some rather unusual individuals—including a memorable, short appearance by Boris Karloff—before focusing on George Sanders and his business associate, Sir Cedric Hardwicke. The former certainly seems like a likely suspect; he openly expresses his romantic interest, and when certain clues appear definitive, Charles Coburn ("Insp. Temple") believes they’ve apprehended the culprit...but have they really? The narrative isn't groundbreaking, but the cast members perform effectively, and while not particularly frightening, the suspense steadily increases toward a cleverly resolved conclusion. Ball portrays a character quite different from those she later became known for, and performs admirably alongside her talented colleagues, a solid script, making this a worthwhile viewing experience.

Source on TMDB