Renowned photographer Ernest Withers captured some of the most stunning moments of the civil rights era—from the age-defining snapshot of Dr. Martin Luther King, Jr., riding one of the first integrated buses in Montgomery, to the haunting photo of Emmett Till’s great-uncle pointing an accusing finger at his nephew’s killers. He was trusted and beloved by King’s inner circle, and had a front row seat to history…but few people know that Withers was also an informant for the FBI.

Memphis journalist Marc Perrusquia broke the story of Withers’ secret life after a long investigation culminating in a landmark lawsuit against the government to release hundreds of once-classified FBI documents. Those files confirmed that from 1958 to 1976, Withers helped the Bureau monitor pillars of the movement including Dr. Martin Luther King and others, as well as dozens of civil rights foot soldiers.

Now, on the fiftieth anniversary of King’s assassination, A Spy in Canaan explores the life, complex motivations, and legacy of this fascinating figure Ernest Withers, as well as the dark shadow that era’s culture of surveillance has cast on our own time.

From an article by Robbie Brown that appeared in the New York Times under the headline: "Civil Rights Photographer Is Unmasked as Informer for F.B.I." on September 14, 2010, we learn that "a clerical error appears to have allowed for Mr. Withers’s identity to be divulged: In most cases in the reports, references to Mr. Withers and his informer number, ME 338-R, have been blacked out. But in several locations, the F.B.I. appears to have forgotten to hide them. The F.B.I. said Monday that it was not clear what had caused the lapse in privacy and was looking into the incident."

Civil rights leaders have responded to the revelation with a mixture of dismay, sadness, and disbelief. “If this is true, then Ernie abused our friendship,” said the Rev. James M. Lawson Jr., a retired minister who organized civil rights rallies throughout the South in the 1960s. Others were more forgiving. “It’s not surprising,” said Andrew Young, a civil rights organizer who later became mayor of Atlanta. “We knew that everything we did was bugged, although we didn’t suspect Withers individually.”

In support of Young's observation as to the scrutiny under which the Movement labored, David J. Garrow, a Pulitzer Prize-winning historian who has written biographies of Dr. King, said many civil rights workers gave confidential interviews to the F.B.I. and C.I.A., and were automatically classified as “informants.” The difference, Mr. Garrow said, is the evidence that Mr. Withers was being paid.

A Spy in Canaan is as much an outing of a trusted confidant as it is an example of the fallacy of democratic principle.