Setting: World War I, primarily in the United States
 
Focus: German espionage and sabotage efforts on American soil
 
Main Character: NYPD Captain Tom Tunney
 
Role: Leader of a team dedicated to uncovering and stopping German spies
 
Key Themes:
 Espionage and counter-espionage during wartime
 The impact of German sabotage on American industries and infrastructure
 The tension between national security and civil liberties
 
Narrative Style:
 Blends meticulous historical research with a novelistic, suspenseful narrative
 
Significance:
 Sheds light on a little-known chapter of American history
 Explores the challenges and intricacies of domestic security during a global conflict
 
Additional Elements:
 Detailed accounts of specific espionage plots and how they were thwarted
 Insight into the methods and motivations of both the German agents and the American counterintelligence efforts
 Richly drawn characters and vivid scenes that bring the historical period to life
 
Overall: A compelling read for history buffs and fans of spy thrillers, highlighting the hidden battles fought on American soil during World War I.