Ever eager to expand the influence of France's leading gastronomic guidebook beyond her native shores, the Director of Le Guide has been cultivating a useful transatlantic connection in the form of a certain Mrs Van Dorman. Ex-parfumier, presently a publishing magnate and, in her spare time,a fan of private-eye novels, Mrs Van Dorman has deserted the relative safety of La Grande Pomme to accompany a group of crime writers to a recreation in Vichy of a banquet given by Alexandre Dumas before he started work on yet another sequel to The Three Musketeers. And who better to escort her than Monsieur Pamplemousse, Surete sleuth turned top-rank gourmet? Monsieur Pamplemousse himself could think of a number of more suitable candidates, especially when it becomes apparent that the assignment involves a grand entry dressed as d'Artagnan, mounted on an uncomfortably rampant black charger. But when cyanide turns out to be a surprise ingredient of the murder tour it is soon clear that Monsieur Pamplemousse - aided by the unerring nose of bloodhound Pommes Frites - is the only man for the job...