Verity Browne returns from Prague, where she is reporting for the New Gazette, with suspected tuberculosis. Lord Edward Corinth to whom she is engaged is naturally desperately anxious about her.The only cure for TB in 1938 is rest and a healthy diet so he suggests she go to a private clinic in Henley-on- Thames run by a Cambridge friend of his, Dr Leonard Bladon.

It is convenient for Edward as he can keep an eye on her while he investigates the sadistic murder of his dentist, Eric Silver whose death has a Henley connection. Edward had been his dentist's last appointment during which Silver had told him that he believed three elderly patients of his had been murdered. What was more, Silver had identified an entomological connection between the killings. General Lowther had had a heart attack drinking a wine called Clos des Mouches, Hermione Totteridge, a well-known gardener, had been poisoned by the new insecticide with which she had been experimenting, and James Herold had been stung to death by his bees. All three had lived in or near Henley. Edward goes to stay with his old friend Harry Makin who had recently come back to England from Africa as he had inherited a title and a property in Henley. Edward's investigation comes to a thrilling climax during what many believe will be the last Henley Royal Regatta before a new European war. Both Edward and Verity face death from someone or something wicked.