It all began with a dirty panama hat. How best to clean it? The sales staff at the exclusive salon, Christophe et Cie, finally decided on oxalic acid as the best method of removing the offending marks. They weren't to know it at the time, but it was also to prove the best method of murdering one of their colleagues.

The unfortunate Miss Don had been in line for a plum job at the company's new branch in Deauville, and there had been considerable speculation as to whether she or the universally disliked Miss Gregory would be chosen. But shortly after learning that she would be the one to remain in London, Doon was to die an agonising death at the hands of a poisoner.

Young Mr Charlesworth from Scotland Yard, a man uncomfortably susceptible to the charms of ladies, is called in to unravel this increasingly muddling and complex case, only to find his task further complicated by the fact that all his chief suspects are female! But before he has identified the culprit there is another poisoning ...