False Scent
Ngaio Marsh Audio Book

Mary Bellamy, ageing darling of the London stage, holds a 50th birthday party; a gala where she has assembled everyone who loves her and fears her power. Then someone uses a deadly insect spray on Mary instead of the azaleas. The suspects, all very theatrically, are playing the part of mourners and Superintendent Alleyn has to find out which one has played the part of the murderer.