In 1920s London, the Honourable Cressida Fawcett, known for her love of interior design and martinis, visits a friend’s mansion in the countryside, recently the site of a diamond heist. After the death of a chandelier cleaner named Harry, which initially appears to be an accident, Cressida suspects foul play. Discovering a torn piece of silk near the body, she links the murder to the theft, believing the diamonds were hidden in the chandelier. As the investigation unfolds, another guest is murdered, trapping everyone in the mansion with a killer among them. Cressida will have to use her keen observation skills to solve the case before another life is lost.