“Intriguing account of the unraveling of the German intelligence network in the U.S.... thrilling.”

– Wall Street Journal

“Peter Duffy absorbingly recounts the true story of William G. Sebold… right on target.”

– The New York Times

“Rich with eccentric characters, suspense, and details of spycraft in the war’s early days…. The result is a compelling cultural history with all the intricacy and intrigue of a good spy novel.”

– Boston Globe

“Thrilling, well-researched, well-told, fascinating.”

– Minneapolis Star Tribune

"Peter Duffy brings out of the cold — well, out of the shadows — a spy who is not only a hero like Bond, but also a man who was never there... Duffy allows the reader not only into the innermost workings of the investigation, but also to connect with the protagonist Sebold and see the aftermath in a truly human hero."

– Pittsburgh Post-Gazette

"Double Agent is worth reading."

– Washington Post

"The intrigues of Sebold and his minders, vividly depicted by Peter Duffy, read at times like a John le Carré novel. There is a gray, dank sense of boredom in a spy's daily existence, along with a frisson of reckless endangerment, both of which Duffy conveys through a plethora of historical detail."

– Bookreporter.com

"Immensely readable... Colorful personalities proliferate throughout the narrative, the understated character of Sebold gleams. An entertaining work duly informed by Duffy’s knowledge of both the war and New York City."

– Kirkus

"One of the great spy missions of American history."

– Publishers Weekly

"Duffy tracks Sebold’s efforts with a tense, exciting narrative filled with a motley collection of characters, some sinister and some unlikely as villains. This has all the elements of a fine spy novel, with the bonus that it is all true."

– Booklist

"Peter Duffy’s Double Agent exposes the shocking extent of German espionage in America on the eve of World War II with dazzling new research and deft historical insight. A riveting non-fiction thriller that exposes history’s neglect of William Sebold, an unjustly forgotten American hero. Duffy offers still relevant insights into the boundaries of civilian surveillance and FDR’s and J. Edgar Hoover’s handling of intelligence information to influence public opinion."

– Jerrold L. Schecter, Cold War historian and coauthor of The Spy Who Saved the World: How a Soviet Colonel Changed the Course of the Cold War

"Duffy tracks Sebold’s efforts with a tense, exciting narrative filled with a motley collection of characters, some sinister and some unlikely as villains. This has all the elements of a fine spy novel, with the bonus that it is all true."

– Booklist

"One of the great spy missions of American history."

– Publishers Weekly

"Double Agent is an important and impressively researched account of a still little-known man who made a big difference in the world of counterintelligence. Duffy reveals new information, much of it from thousands of pages of FBI documents... Both timely and significant."

– Dan's Papers, (Hamptons)

"The grip of good fiction and the punch of hard truth."

– Chicago Tribune