Correction appended Oct. 17.
After serving almost 10 years in prison, David Greenglass vanished into pseudonymity in 1960 with one wish: “All I want is to be forgotten.”
As an Army machinist assigned to Los Alamos during World War II, Greenglass–who died in July at 92 but whose passing was only revealed on Oct. 14–stole atomic-bomb secrets for the Soviets. He later confessed, and to spare himself and his wife, he implicated his sister Ethel Rosenberg and her husband Julius.
Years later, Greenglass told me he had falsified the most damning evidence against his sister, who was executed with her husband. Greenglass was remorseless when we spoke, still convinced that “as long as they had something over my head about my wife and my family, they could probably get me to do anything that would preserve them … And most men would do that.”
Greenglass won’t be forgotten. He’s a Woody Allen punch line about misplaced sibling love. He will forever be remembered, he admitted to me, as “the man that had his sister and brother-in-law put to death.”
Roberts, a New York Times correspondent, is the author of The Brother: The Untold Story of the Rosenberg Case
Correction: An earlier version of this article incorrectly named Greenglass’s sister. She is Ethel Rosenberg.
This appears in the October 27, 2014 issue of TIME.