The Riddle of the Sands (1903) by Erskine Childers is regarded as one of the earliest spy novels. The story follows two young Englishmen, Carruthers and Davies, who embark on a sailing holiday along the Frisian coast of Germany. What begins as a leisurely yachting trip turns into a mission of national importance when they uncover a secret German plot to invade England across the North Sea. Blending vivid sailing detail with suspense and patriotism, the novel warned Britain of its naval vulnerability. Remarkably prescient, it anticipated the German threat preceding World War I and became a classic of espionage fiction.
