[2] Fuchs was a German physicist who is best known as an atomic spy, who passed secrets to the Soviet Union while working on the Manhattan Project during World War II.

[4] Fuchs pleaded guilty to violating the Official Secrets Act of Great Britain on 2 February 1950 and subsequently served a nine-year prison sentence.

[3] The book was reviewed in Nature by Sharon Weinberger,[3] in The Wall Street Journal by Henry Hemming,[5] in The New York Times by Ronald Radosh,[1] and in the Indian newspaper The Wire by Rudrangshu Mukherjee.

[4] In a review by Publishers Weekly, the book was said to be "circumspect" and "richly detailed", with prose that is "more diligent than dynamic", but that it "builds tension by interweaving Fuchs’s scientific and espionage pursuits with MI5’s efforts to unmask him".

[6] Kirkus Reviews wrote that the book "focuses much attention" on Fuchs' early life, "emphasizing his activism over his research and portraying a likable if bland character who regretted only betraying his friends".

[12] In her review, Sharon Weinberger wrote that the book "weaves extensive archival research into a deeply nuanced and sympathetic portrait of a scientist-spy with the best of intentions"[3] and that "even those who might disagree with Thorndike Greenspan’s charitable portrayal will find much to appreciate about a narrative that captures the heated politics of an era with lessons for our own.