Inspector Sloan, accompanying his wife Margaret to a prenatal examination, is rescued by Dr. Dabbe, who is about to perform an autopsy on Beatrice Wansdyke, 59-year-old chemistry teacher at a girls' school. She supposedly died of diabetes, which wouldn't interest the Berebury force, and with a quarter of a million pounds in the bank, which interests them very much. Where could she get that kind of money - legally or illegally? The bank surely isn't saying, and the police force isn't familiar with her, except for Crosby, who was sent out when she reported a lost dog a few days ago.

Her nephew George, a director of the plastics company where Miss Wansdyke did research when away from teaching, hasn't been told why the coroner ordered a post-mortem, but he's too wise in the ways of legal authority to protest. Her niece Briony, now free to quit her nurse's training and marry whenever she likes, is worried over something - her brother Nicholas, the family black sheep. Dabbe's autopsy reveals that Miss Wansdyke did indeed die of diabetes - but that doesn't mean it wasn't murder. Especially when Crosby finds the dog with its throat cut in Miss Wansdyke's back garden...

Sloan is less than keen about this case, since his wife's obstetrician is engaged to one of the suspects, and their first child is due to be born any minute.