As World War II blazed across Europe, numerous Allied airmen found themselves shot down and having to escape German-occupied territory. To assist them, resistance groups sprang up dedicated to guiding them back to safety. This riveting history tells the story of the largest of these, the Comet Line, following the journey of a pilot named Robert Grimes and the helpers who led him across the Pyrenees. Written in a style that evokes spy novels, Peter Eisner’s book pays close attention to the physical sensations of the journey—crackling rains, flooded rivers, snow-swept mountains—to create a sense of immediacy. The villains and traitors are satisfyingly, almost cinematically, wicked, while the book’s central mystery—what motivated ordinary people to risk their lives on behalf of strangers—lingers long after the story is finished.