Tears of Autumn — Charles McCarry

Paul Christopher, at the height of his powers as a secret agent, believes he knows who arranged the assassination and why. His theory is so destructive of the legend of the dead president, though, and so dangerous to the survival of foreign policy that he is ordered to desist from investigating. But Christopher is a man who lives by and for the truth, and his internal compunctions force him to the heart of the matter. He resigns from the Agency and embarks on a tour of investigation that takes him from Paris to Rome, Zurich, the Congo, and Saigon. Threatened by Kennedy's assassins and by his own government, Christopher follows the scent of his suspicion -- one breath behind the truth, one step ahead of discovery and death.