First published as a book in 1924 and thus out of copyright this year, Talbot Mundy’s “The Nine Unknown” is an occult thriller for fans of the Indiana Jones movies, Dan Brown’s “The Da Vinci Code,” Rudyard Kipling’s “Kim” and, of course, Mundy’s other supernaturally inflected adventure classics, “King — of the Khyber Rifles” and “Om: The Secret of Ahbor Valley.” Set in India, the novel focuses on a secret society — the Nine Unknown — that has existed for centuries, accumulated immense wealth and used its esoteric powers to shape the course of history. As one character says, “Viceroys, kings, and all their pomp are side-shows.”

In search of the Nine is an international cadre of heroes: the learned priest Father Cyprian, the American adventurer James Schuyler Grim (who “had never been praised by anyone except his enemies”), the old India hand Athelstan King, devil-may-care street magician Jeremy Ross and the superstrong Jeff Ramsden. Those are the westerners, but just as important are the resourceful Hindu Chullunder Ghose, the Pathan mercenary Ali of Sikunderam — “I cut throats with an outward thrust” — and the Sikh warrior extraordinaire Narayan Singh. Nearly all these colorful characters reappear in other Mundy novels, including a loose sequel to this one set in Tibet, 1926’s “The Devil’s Guard.”

The action begins with a pouch of gold coins, none of more recent date than a thousand years B.C. Their owner, a Portuguese named Da Gama, tells Father Cyprian, Grim and the others about the Nine. Each of the Nine is known only to the other eight. Each, in his turn, employs nine lieutenants and each lieutenant oversees nine underlings and so on, reaching a total of 729 operatives, “each of whom knows only eight, at most, of his associates, but all of whom are at the service of the Nine, whom they know neither by sight nor name.”

While Mundy’s adventurers are chiefly interested in the Nine’s gold and treasure, Father Cyprian is after their books. Not their account books, but the nine volumes that contain the sum of their hermetic knowledge and reveal the secrets of the ancient mysteries. He aims to burn the unholy things — once he can find them. As it stands now, the Nine appear to be ushering in what the Sanskrit scriptures prophesied as the “Kali Yug,” the age of darkness.

Before long, Da Gama disappears. Rather than reveal too much more, let me just say that the rousing chapters that follow involve eerie priests in orange-yellow smocks, the alchemical mantra “As above, so below,” silken handkerchiefs that kill, an Indian brothel, hypnosis and poison gas, the human incarnation of the death-goddess Kali, telepathy via the “Silent Call,” a corpse that speaks and a startling revelation about the holy Ganges River. Most important of all, Grim and the others gradually begin to wonder about the true nature of their adversaries.

Given that “The Nine Unknown” initially appeared as a serial in Adventure magazine, its breathless narrative pace and the prevalence of cliffhangers should come as no surprise. However, Mundy does demonstrate one stylistic idiosyncrasy. While the novel’s action is related in the past tense, the unnamed narrator inserts additional comments in the present tense. Thus: “Jeremy took twenty sovereigns from his belt. (He always carries them, they constituting his uttermost reserve, never to be spent, but to be bluffed with.)” Such temporal shifts suggest that Mundy’s heroes actually exist and that, despite seemingly insuperable odds, they will still be alive when the book ends.

Throughout, Mundy leavens the rush of violence and growing suspense with urbane cynicism: “The street was as peculiarly empty as it sometimes is when a royal personage is due for assassination.” Cyprian, knocked unconscious, is found “smiling like a man who sees beyond the veil and is agreeably surprised.” The narrator observes that “there is nothing in the world more sure than that the priests and politicians always abandon their clients when convenient; nor anything more fixed than the assurance of the due-to-be abandoned until the miserable fact confronts them.”

Mundy’s two best-drawn characters, Ali and Chullunder Ghose, are nobody’s fools, but they do provide comic relief. For instance, the latter achieves wonders of extravagant floridity: “For if an earthquake had emptied Bedlam, releasing affinities of swine of Gadarenes . . . that would be diamond-edged sanity compared to this! This is worse than acting on advice of experts! This is — oh, my aunt!” A little of Chullunder goes a long way.

Unlike some writers of what used to be called “Oriental adventure,” Talbot Mundy despised colonialism, admired India’s culture and came to believe in both karma and reincarnation. Just after finishing “The Nine Unknown” he joined the Point Loma Theosophical Community near San Diego, studying there for many years. Much of his later fiction consequently blends pulp derring-do with a theosophical subtext. For this reason, that much-missed scholar, Brian Taves, titled his authoritative biography, “Talbot Mundy, Philosopher of Adventure.”

Until his death in 1940 at age 61, Mundy remained a hardheaded and successful, professional writer. Besides exciting quest-romances and espionage thrillers, often set in India, Tibet or the Middle East, he also produced the sword-and-sandal historical romance “Tros of Samothrace” and churned out hundreds of scripts for the popular radio series “Jack Armstrong, the All-American Boy.”

Mundy’s “The Nine Unknown” is just one of several highly entertaining novels published in the United States in 1924 and now in the public domain. Let me also recommend Lord Dunsany’s beautifully written romantic fantasy “The King of Elfland’s Daughter,” P.C. Wren’s Foreign Legion swashbuckler, “Beau Geste,” Edgar Rice Burroughs’s “The Land That Time Forgot,” Francis Brett Young’s spooky “Cold Harbour,” and such golden-age mysteries as Edgar Wallace’s nostalgically kitschy “The Green Archer” and A.E.W. Mason’s “The House of the Arrow.” Any of these books will provide at least temporary respite from the nightmare in which we now live.

Michael Dirda reviews books each Thursday in Style.

THE NINE UNKNOWN

By Talbot Mundy