I believe that a well-known anecdote exists to the effect that a young writer, determined to make the commencement of his story forcible and original enough to catch and rivet the attention of the most blasé of editors, penned the following sentence: “ ‘ Hell!’ said the Duchess.” Strangely enough, this tale of mine opens in much the same fashion. Only the lady who gave utterance to the exclamation was not a Duchess! It was a day in early June. I had been transacting some business in Paris and was returning by the morning service to London where I was still sharing rooms with my old friend, the Belgian ex-detective, Hercule Poirot…