In London, Scotland Yard investigators receive the latest in a series of cryptic poems authored by an elusive killer and conclude that his seventh victim will be a dancer. Inspector Harley Temple of the Criminal Investigation Department orders a typewriter and fingerprint analysis of the poem, but the identity of the "Poet Killer," as he has been named, eludes investigators. While the police investigation continues, English dance hall hostess Lucy Barnard and American dancer Sandra Carpenter are offered auditions by producers Robert Fleming and Julian Wilde for their new stage show. Though Sandra accepts the offer, Lucy refuses and explains that she is quitting the dance hall circuit to travel with a handsome man she met through a personal advertisement. When Lucy disappears a short time later, Temple believes that she has fallen victim to the killer. After locating Sandra, the last known person to have seen Lucy, Temple hires her to act as a decoy to trap the killer. As part of her assignment, Sandra sets out to answer all the personal advertisements in the newspaper in which pretty women are sought. After an introduction to an assortment of strange men, including an eccentric artist who at first appears menancing but turns out to be harmless, Sandra answers an advertisement that leads to a job as a parlor maid for aristocrat Lyle Maxwell. Meanwhile, Fleming, an irrepressible playboy, orders his assistants to find Sandra, whom he has not met, but whose beautiful telephone voice has enchanted him. Robert meets Sandra by coincidence one evening when they both attend the same concert. The two fall instantly in love and become engaged, but soon after moving into Robert's home, Sandra finds evidence indicating that Robert knew Lucy. Temple, meanwhile, has discovered a passage in the latest poem he received from the killer that suggests that Robert is the culprit and that Sandra is his next intended victim. Robert is arrested, and although he is innocent, he refuses to defend himself at his trial because he feels that Sandra has betrayed him. Temple later suspects that Robert is being framed by someone else and, with Sandra's help, proves that Wilde, Robert's housemate, is the real killer. Wilde's guilt is revealed in time to save Robert from execution, and Robert resumes his romance with Sandra.