A young president was dead, a nation grieved, and James Grady of Montana, all of fourteen in November 1963, started, for the first time, to entertain doubts. Doubts about the order of the universe as he understood it. Doubts about what underlay the American experiment. Doubts about his government. Doubts about what he could see just ahead, and what trailed just over his shoulder...

This inchoate sensation – that not everything was as it appeared, and that ordinary Americans were unwittingly ensnared in invisible and often lethal intrigues – instilled in the aspiring novelist a particular fascination with the murky world of espionage. As the tempo of the Sixties accelerated, and many in and out of media and government began raising questions about the Warren Commission's official conclusions about the assassination of President Kennedy, Americans' attention turned, as never before, to the U.S. intelligence community: its structure, its operations at home and overseas, its internecine rivalries and alternately dark and comic cast of characters.

All of this Grady channeled into his debut novel, published in 1974 and entitled "Six Days of the Condor." It followed a young and mostly bored CIA analyst named Ronald Malcolm, code-named Condor, whose job was to read spy thrillers and technical manuals, the most tedious literature emanating from the Soviet Union, scouring for possible intelligence and counterintelligence plots of which American spies might need to be apprised. One afternoon, after Condor has enjoyed a lunch break on Capitol Hill, away from the non-descript townhouse where his analytical unit was based, he returns to find all of his colleagues gunned down at their desks – and that he is the assassins' next target. The intrigues that follow reveal that Condor is as much on the run from murderous elements within his own spy service as from external threats.

"Starting with the assassination of John Kennedy," Grady told me in a recent visit to "The Foxhole," "we became aware that there were forces that were not in the daily news, that were not – that investigative reporters like you were not being able to bring to the public attention. That was heightened, of course, by the Vietnam War that was – began as a lot of intelligence operations bundled into a military response. And I think the awareness of that, which was really nascent, really small at the time, captured my imagination and when I came – when it came time for me to put up or shut up and actually become a writer, which happened very young for me, I was just so swept away by these [doubts] – this [sense of] ‘What is going on out there in the Unknown World that is affecting every citizen like me?'"

"Six Days of the Condor" became a huge bestseller, and, in short order, an iconic, Oscar-nominated film entitled "Three Days of the Condor" (1975), starring Robert Redford – then at the height of his mid-Seventies fame – and the ravishing and ultra-sophisticated Faye Dunaway. The book and movie fused together in the public mind to form one of the foundational texts for the paranoiac sensibility that marked the Watergate era, along with the films The Parallax View (1974), starring Warren Beatty; Francis Ford Coppola's mid-Godfather thriller, "The Conversation" (1974), starring Gene Hackman; and of course "All the President's Men" (1976), which also starred Redford.

Amid all this James Grady, only twenty-three, abruptly found himself one of America's most celebrated novelists, an instant demigod of the spy genre who found all doors open and received cherished sotto voce counsel from previously untouchable heroes like John le Carré and Robert Ludlum ("Keep working," they told him, wisely). Grady published a sequel, entitled "Shadow of the Condor" (1975), which expanded the action geographically to include the Soviet Union and Communist China, but then – rethinking his initial vision of publishing five Condor novels in all, spaced two years apart – Grady let Condor go altogether. For forty years.

"When the [first] book came out, I had absolutely no idea it was going to be such a massive hit," he told me. "And then, to be followed by Robert Redford making really an iconic movie…I realized I don't want to compete with Robert Redford and that great work of art they did. So I had to let it go and go on and do a number of other novels."

ROSEN: You felt in competition with the movie?

GRADY: I didn't want to – I didn't want to get to that place. I felt that at some point if I kept going with the Condor series that close to the movie's release, it'd be an inevitable comparison. And I wanted to give both my literary character and Redford's iconic cinematic character their own space to breathe….You create a completely imaginary entity in your head, this human being, and he takes on a shape that you sort of recognize. And then you'll see an artistic depiction and you'll go, "Well, I don't think he's that good-looking. I don't think he's that tall." But it serves the purposes of, of –

ROSEN: But the checks clear, and – [laughs]

GRADY: Most of them did, yes! [laughs]

An even scarier phenomenon emerged when it was brought to Grady's attention that the specific plot device he had employed for the killing scenes in "Six Days," involving a disguised mailman, had been appropriated and used – to devastating effect – by Iranian spies to murder an Iranian dissident living in Bethesda, Maryland, not far from Grady's own home.

A former legman for the late syndicated muckraker Jack Anderson, Grady spent the next few decades writing screenplays. He found himself, to some extent, a prisoner of his own success; publishers repeatedly greeted his manuscripts with the fatiguing insinuation: "This is great; but can't you give us another Condor?" It got so bad that Grady published his 2000 novel, "City of Shadows" – a reimagining of the Watergate break-in through the prism of an alternate theory of the case, one that posited that the ill-fated surveillance operation at the Democratic National Committee headquarters was actually targeting a call-girl ring said to be doing business with the DNC – under a pseudonym.

Along the way, he dabbled at the resurrection of Condor, publishing after 9/11 some passages inspired by the terrorist attacks under the domain of www.condor.net, which today links directly to www.jamesgrady.net. Now, Condor is finally back in earnest – no longer boyishly ambivalent, as in the early Seventies, but graying in his middle sixties, freshly released from a CIA insane asylum, disgorged into a dramatically altered world of technology and digital communications,  and once again on the run from assassins who believe that Ronald Malcolm, to borrow a phrase infamous from Watergate, knows too damned much. The venue is Grady's (maybe) final installment of the series, "Last Days of the Condor", published this year by Forge Books/Tom Doherty Associates. (A short prequel, "Next Day of the Condor," appeared a few weeks earlier as a Kindle e-book, available on Amazon. So, for Condor counters – and Grady makes clear, there are to this day freakish Trekkie-like fans who stop him in public places, eager to explore the tiniest of anomalies in the Condor canon – that makes four installments in all, not counting the passages that ran on condor.net.)

To prepare for the writing of "Last Days of the Condor," the author, like any good investigator, retraced his steps: He reread "Six Days" and "Shadow," brushed up on our era's new hi-tech gadgetry, and thrust himself back, once more, into the mind of Ronald Malcolm. Of invaluable aid in the enterprise is the innate suspicion – that old lingering doubt – that still informs Grady's approach to the world of politics and intelligence. "As you and I both know," he told the host of "The Foxhole," the official story is sometimes" – he pauses for a second – "incomplete."

James Rosen joined Fox News Channel (FNC) in 1999. He currently serves as the chief Washington correspondent and hosts the online show "The Foxhole." His latest book is "A Torch Kept Lit: Great Lives of the Twentieth Century" (Crown Forum, October 4, 2016).