False Scent (Roderick Alleyn Series #21)

Mary Bellamy is the sweetheart of the London stage. Her fans and friends are heartbroken when somehow Mary manages to spritz herself not with her favorite perfume, but with the deadly insecticide meant to be sprayed on the azaleas. Inspector Alleyn begins by smelling something fishy (everything he learns about lovely, fragile Mary suggests that in fact she was a rather vicious battleax), but he very quickly starts smelling something different…something like a rat.