A key influence on the plot of "The Calculus Affair" was an article that Hergé had read in a February 1954 issue of the Belgian weekly "La Face à Main", reporting that there had been a number of incidents along the road from Portsmouth to London in southern England in which motorists' car windscreens had spontaneously shattered; the article's author suggested that it may have been caused by experiments undertaken in a nearby secret facility.