Floyd, the son of Professor Garden, invites his socialite friends to the rooftop garden of his father's New York penthouse to listen to the outcome of horse races. Detective Philo Vance receives an anonymous telephone message inviting him to one of Floyd's gatherings. On that particular night, Floyd's best friend has placed an enormous bet on a horse named Equanimity. Once it is announced that Equanimity has lost the race, a gunshot is heard and Floyd's friend is found dead of a gunshot wound. Though initially thought to be a suicide, Detective Vancedeems the death a murder. The night proves to be even more eventful, due to the attempted poisoning of Floyd's mother's nurse and the subsequent murder of his mother. Ultimately, Detective Vance is able to solve the murders. He lures the murderer into revealing himself and gathers photographic evidence of him trying to push the detective off of the garden balcony.
Literary significance and criticism
Crime novelist and critic Julian Symons wrote, "The decline in the last six Vance books is so steep that the critic who called the ninth of them 'one more stitch in his literary shroud' was not overstating the case."