"In Mexico they call this and others like it Craneo de Cristal de Roca, which in English means skull of rock crystal. It is at least 4000 years old and took scores of years, generations even, to fashion. It was used by the High Priests of the Maya people as a device to focus and amplify their connection, their communion, with the spirit world. By way of this skull and others like it the High Priest could cure or he could kill. When the High Priest willed death, with the help of the skulls, death inevitably followed." Or at least that is what the rather sinister figure of Mr Pembleton Snoyle has convinced some powerful figures of. He claims to have two out of a total of thirteen skulls, and with the rest he can achieve great things. So Samson Plews and Miss Sha are despatched to find and gather the scattered collection. The trail leads through Paris, under threat from Zeppelins and the Prussian Army, to wartime London, Southern California, and Central America. But of course, matters are never quite as simple as they might seem . . . !