Professor Garden has a New York penthouse with a rooftop garden, and his son Floyd is accustomed to gather a group of socialite friends together in the Garden garden to listen to the results of horse-races over a built-in loudspeaker system. Philo Vance receives an anonymous telephone message that leads him to one such gathering, on a day when Floyd's best friend has placed an enormous bet on a horse named Equanimity. Equanimity loses, and a gunshot takes the life of the friend, but Vance determines that it is murder and not suicide.
