Two men are killed by cyanide poisoning before Bony comes to Broken Hill to take up the case, and a third dies soon after he arrives. All die in crowded public places, and all are elderly and single. Witnesses recall a woman being near each man before he died, but their descriptions seem to be of entirely different women. Clues are old and witnesses have been mishandled by an inept investigator before Bony arrives in the prosperous mining town, but with the help of the local constabulary, a professional burglar vacationing in Broken Hill, and an amateur quick-sketch artist, Inspector Bonaparte mounts an investigation to identify the murderer before she finds another victim.