Lois Meade is boss of a cleaning business, and finds time on the side to indulge her love of sleuthing. She opens an office in nearby Tresham, and is intrigued to see a number of surprising visitors to the small shop on the other side of the street. Their window display tells all! New business comes her way when she is asked to clean the house of Tresham`s pompous and secretive mayor, Howard Jenkinson. A locked room arouses Lois`s curiosity, especially when the mayor`s chauffeur is seen collecting a parcel from the shop opposite. Lois, her daughter, and some of her regular cleaners, gradually uncover lies, adultery and sex for sale. When seemingly harmless goings-on result in death and murder, it is time for her old admirer, Inspector Hunter Cowgill, to become involved. True to form, Lois ignores his warnings and finds her own life in danger.