Spymasters must have long smiled at Henry James’s great description of the novelist – “one on whom nothing is lost.” Where are the Jamesian spy novels? Latin literature is the ideal field. Borges, in his bibliomanic investigations, seems to be wearing two hats, Don Quixote’s poorly constructed sallet and Sherlock Holmes’s invincibly amateurish deerstalker.

In the literature of Borges’s legacy, hunches have become a high road to literature. Now Javier Marias, considered by some to be Spain’s best bait for the Nobel Prize, has found an unexpectedly explicit way to retail the art of fiction as the art of detection. In “Your Face Tomorrow: Fever and Spear” (New Directions, 388 pages, $24.95), he imagines a branch of MI6 that recruits individuals who possess not supernatural but very sophisticated powers of perception.

Jacques Deza, also the hero of Mr. Marias’s novel “All Souls,” describes his job: “This consisted in listening and noticing and interpreting and reporting back, in deciphering behaviours, attitudes, characters, and scruples, indifferences and beliefs, egotisms, ambitions, loyalties, weaknesses, strengths, truths, and contradictions; indecisiveness. What I interpreted were – in just three words – stories, people, lives. Often stories that had not yet happened.” Deza never knows what part of the government has commissioned his report, or why. He is merely presented with a video, or sits in on an interview, and is then asked to report, spontaneously, on what he sees of a subject’s character.

At almost 400 pages, “Fever and Spear” is only volume one of an “unfolding novel” that threatens to be as insurmountable as “The Man Without Qualities.” Yet the events related in this first volume could be condensed into a short story, were it not for Deza’s wildly discursive perceptions. Mr. Marias tellingly equates the “most inspired poet” with the “most zigzagging of narrators.” Deza’s boss, Bertrand Tupra, the sort of man who overtly savors conversation, goads Deza to “Go on. Quickly, hurry, keep thinking and keep looking beyond the purely necessary.”

Deza’s description of this experience sounds like an ars poetica: “to examine in depth what appears to be as smooth, opaque and black as a field of heraldic sable, a compact darkness. Yet one suddenly catches a gesture, an intonation, a flicker, a hesitation.” In lines like these, “Fever and Spear” becomes an essay on the power of following hunches, of quixotic initiative, in finding an adventure where there was none or in answering unasked questions.

Deza comes to dread the creative side of passive observation: “I have learned to fear anything that passes through the mind,” he says. Yet it can’t be avoided; it is what life is made of:

Perhaps that’s all it is, the ending and knowing the ending, knowing what happened and how things turned out, who was in for a surprise and who was behind the deception, who came off well or badly or who came out even or who did not bet at all and so ran no risk, who – nevertheless – came out the loser because he was dragged along by the current of the broad, rushing river, which is always crowded with gamblers, so many that eventually they manage to get all the passengers involved, even the most passive, even the indifferent, the scornful and the disapproving, the hostile and the reluctant; as well as those who live along the banks of the river itself.

The river of time drags Mr. Marias from his tale of espionage into a metaphor out of Mark Twain. Sometimes, this conceit goes too far in justifying loquaciousness. There is little degree of meaning between “the scornful and the disapproving, the hostile and the reluctant”; these lists exist because Mr. Marias insists on the ineluctability of his sentences.

The strange frame Mr. Marias creates for Deza’s reports allows for a wonderful artificiality of characterization. One woman is “desperate for attention, she’d invent the craziest fantasies just to be noticed.” A man is too principled to be bribed, but “might be susceptible to fear, physical I mean, he’s never been punched in his life.” Another is “impetuous and impatient, it’s hard to understand how he can exercise authority over anyone.” These sketches are too succinct, too certain, to sit well with most contemporary literary narrators. That’s why they’re such a treat for the reader.

The success of Mr. Marias’s projected novel will depend on whether this kind of writing – for he is about style, not plot – can continue to bear new fruit over thousands of pages. He has so far underpinned his story with a great deal of pathos, imagining a Jedi like patrimony of persons with Deza’s powers. At length this threatens to cloy into melodramatic, solipsistic spy fiction. By the paragraph, it can be gold.