This mystery has a simple plot but enough layers to make it more than a routine whodunit. For many Peggy Lee fans, I suspect the layers may hold as much interest as the mystery. Of its many characters, the most important is protagonist Peggy Lee, who plays several roles. She is a botanical expert, amateur investigator, friend to many, mother, wife once widowed by a man who was murdered, runs a small business, and provides technical expertise to law enforcement. One of her connections is "Nightflyer," who communicates with her via email, seems to follow her life, and offers oracular advice.
The obvious threads in the novel are the murder mystery; botany (running a gardening shop, offering advice to friends and clients, lecturing, consulting); and personal (interacting with husband, son, expectant daughter-in-law, and an overbearing dog named Shakespeare).
The plot: Prompted by Nightflyer, Peggy tries to link up with a man who may be connected to the death of her first husband, the man dies, Peggy follows leads to investigate the contents of a storage locker, a exhumed corpse yields surprises, a mysterious woman offers Peggy a deal she cannot refuse, she meets the woman, and (revealing the rest would be a spoiler).
The novel is intelligent, well written, and adheres to the usual cozy conventions. As a bonus, it includes botanical vignettes, a recipe for onion soup, and advice on finding edible plants in your garden. Much to this reviewer's surprise, the Lethal Lily of the title turned out not to be what I expected.