The secret letter was tucked inside the pages of an old book. It had been written by FBI Director J. Edgar Hoover to a top lieutenant, condemning civil rights leader Martin Luther King Jr.

It was Nov. 19, 1964, and Hoover the previous day had assailed King at a news conference as “the most notorious liar in the country.” Now he was writing a colleague privately to say he hoped King was getting his “just deserts.”

“I certainly hope so,” Hoover wrote.