By Charles McCarry. Overlook. 476 pp. $25.95

As soon as he began publishing fiction more than three decades ago, Charles McCarry was recognized as a spy novelist of uncommon gifts. He enjoys, like the masters of the genre (Buchan, Greene, Fleming, le Carre), the presumption of authenticity grounded in a prior career in intelligence work. McCarry in his younger days was a CIA agent operating "under cover," the Old Boys jacket flap discloses, before he turned to fiction and a long tenure at National Geographic.

But knowing what you're talking about is not enough. From the outset McCarry has been willing to take risks in both form (the documentary structure of The Miernik Dossier, his first novel, 1973) and content (linking the assassinations, three weeks apart, of Presidents Ngo Dinh Diem and John F. Kennedy in November 1963, in The Tears of Autumn, 1974). Shelley's Heart, more than 20 years later, confirmed McCarry's versatility as a Washington novelist, too, with an eerily anticipatory tale of a stolen presidential election.

In Old Boys, his 10th novel, McCarry has cut loose yet again, this time in a cheerfully convoluted yarn whose tone is by turns mischievous and elegiac.

To set the stage, think of Yul Brynner in the opening scenes of "The Magnificent Seven," recruiting a posse of specialists in each of the lethal arts to take on one last challenge -- because they believe in the cause. The Brynner character in Old Boys is Horace Hubbard, a retired spy of the old school, and the magnificent are six. Their mission is to discover the fate of Hubbard's older cousin, Paul Christopher. Christopher, introduced in McCarry's first two novels, is the recurring spy of his oeuvre, a romantic loner who has recently survived 10 years in a Chinese prison. And now he seems to be dead. Seems to be.

For reasons McCarry can better explain, the fate of nations and the meaning of life are wrapped up in this mystery. As Horace muses in one of the author's many considerate reminders, "The problem now was to establish whether Paul Christopher was or was not a dry quart of ashes inside a gaudy Chinese urn and, far more difficult than that, to accept that this Prince Valiant of my childhood had at last encountered an ordeal he could not survive. . . . Whatever drove him to Ulugqat must have been a matter of great significance, at least in his own mind -- something he felt he absolutely had to do, had to know, had to find in order to make sense of existence." Who better to unravel this than Horace and his fellow-retirees. "Taken together, [we] used to know most of the people in the world worth knowing," he reminds his cronies as he makes his pitch over lunch at a steakhouse on K Street in Washington. They're game.

With Christopher's necessarily beautiful daughter Zarah providing support and, well, youth, the old boys fan out around the world with their timeworn instincts and new-fangled SAT phones. They get in and out of heaps of trouble. They may be senior citizens, but they still know how to deal with bad guys. In Moscow, for example, our man Horace does an impressive turn forcing a thug to break his own neck.

Impending mortality has made them a sentimental bunch: They are interrupting their retirements not to crush terrorists or subvert evil empires -- although these are nice if you can get them -- but because of ties of friendship, of blood-brotherhood and of just plain blood.

The holder of the secret, we learn early on, may not be Paul Christopher at all but his 94-year-old mom, Lori. She may possess -- here McCarry experiences a Dan Brown moment -- a first-century scroll purporting to be "the report of a Roman official sent on a secret mission to Judea around the time of the Crucifixion to investigate a Roman covert action operation that went wrong." The scroll, because it may expose Jesus of Nazareth as "an unwitting asset of Roman intelligence," is coveted by a radical Islamist and recurring McCarry foe, Ibn Awad, as evidence that "Christianity is a false religion." High stakes indeed.

McCarry is a careful plotter and an unfussy stylist; he nourishes his narrative with cosmopolitan reflections on the craft (of espionage, and perhaps of fiction, too) such as this one: "Operations develop like the seduction of a woman who knows that she's worth any amount of trouble -- false moves, faux pas, misunderstandings, rebuffs, zones of silence, long gazes into seemingly candid eyes that will not answer the simplest question. And then, when you have despaired of ever seizing the moment, it arrives." Old Boys is, at heart, a lament for a dying generation of American spies, an elegy for the human twilight, "Cocoon" with a cloak and dagger. Here's how one young Agency whippersnapper -- a woman, no less -- puts it to the old boys: "You're well and gratefully remembered. But you and your old-timer friends are causing a lot of unnecessary trouble. You're getting between our people and an important target. What is desired -- and this comes from the very highest level -- is for you and your shuffleboard team to get out of the way. And stay out of the way." Them, of course, be fightin' words. *

Charles Trueheart, a former Washington Post correspondent, lives in Paris.