New York cop Frank Keller is on the trail of a serial killer who murders men answering personal ads in the classifieds. The ads, written in poetic couplets, are quite romantic, but those who meet their mysterious author end up dead in their own apartments with a 45rpm copy of the '50s single "Sea of Love" on their turntables. Keller, suspecting the murderer is a woman, places his own advertisement in the paper and sets up dinner dates (one every half-hour) with the respondents; he lifts their fingerprints from their wine glasses and matches them against those of the murderer, taken from the crime scene. But Keller's scheme fails when he falls in love with one of the suspects and refuses to check her prints. With each passing day their romance grows hotter... and the growing evidence keeps pointing more strongly to her guilt.