When the body of Violet Feverel is discovered on the Central Park bridle path, Inspector Oscar Piper is about to declare her death accidental from a thrown horse, until his friend and amateur detective Hildegarde Withers locates the horse and discovers blood on the horse. The coroner deems it a murder when the cause of death is shown to be by a blunt instrument on the victim's head. The suspects include Violet's ex-husband, Don Gregg, who she jailed for nonpayment of alimony, but who was just released by a forged court order; Latigo Wells, the manager of Violet's stables and who had an argument with her that morning; and Eddie Fry, who had quarreled with Violet over his seeing her sister, Barbara Foley, and who was about to elope with Barbara. At Don's Long Island home, Hildegarde and Oscar meet his sickly father, Patrick, the caretaker, Chris Thomas, and his crippled son, Joey. After Patrick is murdered, Hildegarde snoops around and discovers clues which pinpoint the murderer, who is out to kill her.