The last paragraph of a letter discovered by a Newport Beach attorney sheds new light on Upton Sinclair. "This letter is for yourself alone," it read. "Stick it away in your safe, and some time in the far distant future the world may know the real truth about the matter. I am here trying to make plain my own part in the story."

The story was "Boston," Sinclair's 1920s novelized condemnation of the trial and execution of Nicola Sacco and Bartolomeo Vanzetti, Italian immigrants accused of killing two men in the robbery of a Massachusetts shoe factory.

Prosecutors characterized the anarchists as ruthless killers who had used the money to bankroll antigovernment bombings and deserved to die. Sinclair thought the pair were innocent and being railroaded because of their political views.

Soon Sinclair would learn something that filled him with doubt. During his research for "Boston," Sinclair met with Fred Moore, the men's attorney, in a Denver motel room. Moore "sent me into a panic," Sinclair wrote in the typed letter that Hegness found at the auction a decade ago.

"Alone in a hotel room with Fred, I begged him to tell me the full truth," Sinclair wrote. " … He then told me that the men were guilty, and he told me in every detail how he had framed a set of alibis for them."