The constant

In the novel "The Constant" by John Buchan, exciting events are narrated that take us into the midst of World War I, where General Richard Hannay is summoned from the battle fronts for a secret mission that will change the course of the war. British intelligence has discovered the existence of a dangerous German spy network operating inside England, and although much of it has been dismantled, the mastermind is still at large, practicing deception and leaking vital information about Allied ...