Writing a book is an all-embracing, step-by-step process—a marathon, not a sprint. And the author’s reward for reaching the finish line is to compose the acknowledgments, a special honor that requires remembering each stage of the book’s progress in order to appreciate who contributed what and when. For Sleeper Agent, I could write a book about the process and the people involved, but for now, I will simply sing some praises.

First, as always, is my agent, Alice Martell, whose wisdom, diplomacy, and diligence are cherished gifts to her writers. There is also Alice’s voice of reality, which is a major motivator. I am indebted to her. Thanks also to her assistant Stephanie Finman.

An exceptional editor respects a writer’s individual style and route, and yet catches potential wrong turns at just the right moment. That’s Bob Bender, my editor, a fine mix of sensitivity and sharp vision. From the start, he understood my determination to unravel the complexities and to answer the long-standing questions about the life of George Koval. He tolerated my spurts of excitement after big discoveries, discouraged occasional attempts to dig too deeply, and knew the best times to inspire endurance. I’m hugely grateful to Bob and to his assistant, Johanna Li.

For the long, demanding years of the project, I was fortunate for the excellent contributions of the following individuals: 

Masha Stepanova’s superb work in finding and translating relevant Russian-language letters, books, and articles provided crucial details in the narrative, such as the story of Koval’s journey back to America in 1940, and the 1953 letters revealing the respect of Soviet military intelligence for his espionage work. In short, Masha is truly remarkable.

Also outstanding is Joanne Drilling, a skilled researcher with a never-give-up approach who uncovered useful, often surprising, details, especially about the spy Arthur Adams and about buried ties in several Soviet spy networks. Loyal and invaluable, she also indexed thousands of pages of FBI reports and compiled numerous timelines, allowing me to discover intersecting events and locations among the players and organizations in the narrative.

Research librarian Alison Gibson, whom I often have called a national treasure, discovered rare publications that helped to unravel a few conundrums, especially regarding Koval’s handler, Benjamin W. Lassen. And her astute awareness of resources potentially useful to the story was priceless. Also treasured is June Zipperian, who reads at least a book a week, proving that the habit of reading nurtures adept skills for critiquing a piece of writing. I’m honored that June has been a first reader for many a chapter I’ve written in four of my books, including Sleeper Agent. And colossal thanks to Marlay B. Price, who read countless pages of FBI reports to flag specific details for me and who joined me on several of the research trips. When a spouse understands the daily work of a writing partner, the seemingly endless hours of solitude in the writer’s life transform from loneliness to fulfillment. Thank you, Marlay.

Next, I am grateful to Duane M. Weiss, who was a military colleague of George Koval’s at both Oak Ridge and CCNY, and who generously shared his stories and memories with me. I thank Bridget M. Vis who, at the beginning of the research, gave the book its working title, “Undetected.” Also, in the book’s early stage, Sari Ewing shared her expertise on ship manifests and ancestry research plus her sheer elation regarding the topic. I thank Sari especially for her quick realization that George Koval’s “A mighty man is he” in his high school yearbook is a line from Henry Wadsworth Longfellow’s poem “The Village Blacksmith.” Gratitude also to Victoria Baird for her excellent translations of Russian articles at the very start of the project. Much appreciation also to Robin Gilbert, Melody Kokensparger, Sonja Cropper, and Ron Ralston who generously helped with tasks in the midst of crucial deadlines. And immense gratitude to James Ralston for his shared knowledge of nuclear physics, to Josh Karpf for his skillful copyediting, and Lisa Healy, for her expertise as head of the S&S book production.

Throughout the research, librarians and archivists were so often helpful. What the future can know about the past is clearly in their hands: the documentary evidence of history in letters, diaries, reports, government documents, personal records, photos, newspapers, magazines, broadsides, and more.

I am grateful to the following: Amy Reytar, archivist at the National Archives, in College Park, Maryland. Dr. Dana Herman and Dr. Gary Zola, director of research and executive director, respectively, of the Jacob Rader Marcus Center of the American Jewish Archives at Hebrew Union College–Jewish Institute of Religion in Cincinnati; and librarian Alice Finkelstein at the Klau Library, at Hebrew Union College. Archivist Ilya Slavutskiy at the Center for Jewish History and YIVO Institute for Jewish Research, in New York City. Head archivist of the City College of New York, Sydney C. Van Nort. Archivist David Clark at the Truman Library. Aaron Novelle at the Institute of Electrical and Electronics Engineers. At Oak Ridge: Teresa Fortney in the Oak Ridge Room at the Oak Ridge Public Library; D. Ray Smith, historian at the Y-12 National Security Complex; Mark Dickey at the Oak Ridge National Laboratory; and Robbie Meyer, at the Manhattan Project National Historical Park. Curator Tom Munson at the Sioux City Public Museum and Kelsey Patterson at the Sioux City Public Library.

Regarding the myriad files sent from the Federal Bureau of Investigation archives by way of the Freedom of Information Act (FOIA), I must thank Leanna Ramsey, the FBI public information officer, who was always as gracious and efficient as the system would allow. Also, thanks to attorney Adam Marshall at the Reporters Committee for Freedom of the Press for advice on how best to use the FOIA for administrative appeals regarding redacted FBI files. And a special thanks to D.C. attorney and author Mark Cymrot.

Other libraries and archives: The New York Public Library Reading Room and Reference Desk, Main Branch. The Municipal Library at 31 Chambers Street in New York City. The New York City Department of Records and Information Services. The New-York Historical Society. The archives at Columbia University, the University of Wisconsin, the University of Notre Dame, the University of Chicago, and the Massachusetts Institute of Technology. New York University’s Tamiment Library. Washington University’s Special Collections. The Galveston Historical Foundation’s archive. The Atomic Heritage Foundation. The Wright Memorial Public Library. The National Museum of Nuclear Science & History. The National Academy of Sciences Archives. The US Department of State, Passport Office. The New York Times archive. The Central Archives for the History of the Jewish People, in Jerusalem. Ancestry.com. The Mound Science and Energy Museum in Miamisburg, Ohio. The General Electric digital archive. The Massachusetts Land Records site. The Ohio Northern University Archives, Heterick Memorial Library. Pinsk City Archive. Freedom of Information Act Reading Room 

Regarding Russian resources, I am grateful to Maya Koval, George Koval’s grandniece, especially for sending me excellent photos, including one of George’s copy of Leaves of Grass with his signature in 1931 on the frontispiece. And I respect the Russian scholars Aleksandr Petrovich Zhukov and Yuri Aleksandrovich Lebedev for their research and writings about George Koval—plus a posthumous thanks to Vladimir Lota, the GRU historian who also wrote extensively about Koval. Thanks also to Dr. Stephen Norris, the director of Miami University’s Havighurst Center for Russian and Post-Soviet Studies, and Russian language professor Dr. Benjamin Sutcliffe, also an interpreter at the Center—both so very helpful.

       For generous assistance in specific parts of the research, I am grateful to the following: Don and Brian Connelly, Ron Ellis, Peter Fischer, Corey Flintoff, Matthew Francis, Richard Hacken, Peter Houk, David Katzman, Paul Lamberger, Mark Neikirk, Lori Stacel, Michael Stallo, Jim Tobin, Bill Tuttle, Jim and Ann Veith, Jon Warner, and Jocelyn Wilk. Special thanks also to: Chase Beach, Scott and Sarah Byers, Richard Campbell, Scarlett Chen, Jenny and Perry Clark, Nick and Nina Clooney, Jeremiah Costa, Jeffrey and Carol Donohoo, Ceílí Doyle, Lynn Fraze, Tim and Christine Gilman, Lisa Haitz, Pam Houk, Mark Jones, Tom and Alice Laurenson, Lois Logan, Keith McWalter, Joe Prescher, Chris Singer, Emily Williams, Joe Worrall—and a posthumous thanks to George W. Houk.

I must close with a note of gratitude to my editors from many years ago at The Wall Street Journal—Don Moffitt, Norm Pearlstine, Paul Steiger, and Steve Adler—from whom I learned the enduring discipline of a daily writing routine and the value of humility.