Los cigarros del faraón
As with Hergé's two previous stories, "The Secret of the Unicorn" and "Red Rackham's Treasure", "The Seven Crystal Balls" was designed as part of a twofold story arc, to be concluded with the then yet unnamed "Prisoners of the Sun". Hergé planned for the former story to outline a mystery, while the latter would see his characters undertake an expedition to solve it. His use of an ancient mummy's curse around which the narrative revolved was inspired by tales of a curse of the pharaohs which had been unearthed during the archaeologist Howard Carter's 1922 discovery of Pharaoh Tutankhamun's tomb. This was not the first time that Hergé had been inspired by this tabloid story, having previously drawn from it when authoring "Cigars of the Pharaoh".