Richard Hannay is recalled from the front lines of World War I to dismantle a clandestine network of German spies operating within the Allied sphere. Hannay must navigate a web of deception while tracking his elusive adversary, Morton Ivery, across a landscape spanning England, Scotland, France, and Switzerland. The narrative follows Hannay as he assumes various identities to infiltrate enemy circles, facing constant threats to his safety and the security of the war effort. The story utilizes a traditional third-person perspective to detail the high-stakes pursuit and the logistical challenges of intelligence work during the conflict.

Readers frequently highlight the rapid pacing and the effective use of suspense that characterizes the Richard Hannay series. Discussion often centers on the author's ability to blend realistic military history with the conventions of early twentieth-century spy fiction. Critics note that the book maintains a consistent tone of urgency while exploring the moral complexities of wartime duty. The character development of Hannay is often praised for its evolution from a soldier to a sophisticated operative, providing a grounded anchor for the fast-moving plot.