After a close friend's apparent suicide, Christopher Cornwell receives several photos the friend mailed prior to his death. Cornwell subsequently discovers by chance the presence in one of the photos of Lee Harvey Oswald, the alleged assassin of President Kennedy. But how could Oswald be photographed in a small Hertfordshire market town when he was supposed to be living in Russia as a defector at the same time?

As Cornwell investigates the story behind the photos he unknowingly becomes the target of an investigation himself, by a shadowy agency as determined to maintain its secrets now as in 1963.