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. [in] 1964. 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." Four years later, King would be assassinated. And the letter ... sheds yet more light on the historic malice the FBI director had toward King. Washington scholar James L. Swanson said he found the letter ... clipped to a page in [a book] he purchased. "This is a hitherto unknown and unpublished letter," Swanson said. "What happened was this: It was announced [the previous month] that Dr. King had been awarded the Nobel Peace Prize, and that provoked Hoover," he said. Hoover believed that King and his movement were threats to the social order. The FBI had begun wiretapping King's home and office, and bugging his hotel rooms. No serious links to communism were uncovered, but hints about King's sexual dalliances allegedly were. Days after Hoover's news conference, a salacious anonymous letter was delivered to King's wife. This letter was ... in a package that also [contained] a tape recording that allegedly captured evidence of King's sexual misconduct. King suspected that the FBI was behind the letter. Sullivan ... later admitted his involvement in the plan during testimony before a Senate committee.