The Riddle of the Sands: A Record of Secret Service

is a 1903 novel by Erskine Childers and the prototype of all modern spy novels. The book, which enjoyed immense popularity in the years before World War I, is an early example of the espionage novel and was extremely influential in the genre of spy fiction.

When an amateur British sailor on a yachting holiday in the Baltic stumbles upon a German invasion plan masterminded by a renegade Englishman, he must choose between warning his country and his love for the traitor's daughter.