The Sign of Silence (1917)

Popular novel, first published in 1917. According to Wikipedia: "William Tufnell Le Queux (2 July 1864 London - 13 October 1927 Knokke, Belgium) was an Anglo-French journalist and writer. He was also a diplomat (honorary consul for San Marino), a traveller (in Europe, the Balkans and North Africa), a flying buff who officiated at the first British air meeting at Doncaster in 1909, and a wireless pioneer who broadcast music from his own station long before radio was generally available; his claims regarding his own abilities and exploits, however, were usually exaggerated. His best-known works are the anti-German invasion fantasies The Great War in England in 1897 (1894) and The Invasion of 1910 (1906), the latter of which was a phenomenal bestseller."