On the Case With the Navajo Tribal Police : A THIEF OF TIME<i> by Tony Hillerman (Harper & Row: $15.95; 224 pp.) </i>

Tony Hillerman’s mysteries featuring Lt. Joe Leaphorn and Officer Jim Chee of the Navajo Tribal Police are unique in American crime fiction.

They combine a deep and sympathetic knowledge of ancient Navajo beliefs, a poet’s power to evoke the peculiar austere beauty of the Navajo country and a wire service reporter’s sad awareness of the greeds, hates and schemings of the modern world.

In Hillerman’s beautifully constructed plots, the ancient beliefs sometimes seem to have a bearing on present dastardly events, and they certainly color the thought processes of his policemen. But in the end, the crimes are very much from time present, as real and ugly as corpses and never falling back on the mystical to explain the inexplicable.

“A Thief of Time” is Hillerman’s ninth novel and the eighth of his Navajo mysteries. (His second novel, “The Fly on the Wall” in 1971, was a first-rate thriller about political corruption, drawing upon his days as a wire service bureau chief in two state capitals.)

A feisty young woman, an anthropologist digging near the ruined cliff-dwellings up Chinle Wash off the San Juan River, disappears. Joe Leaphorn, although still demoralized by the death of his young wife, takes up the search. It leads him into the world of the pot-stealers, the thieves of time who ransack burial sites and other traces of the Indian past for relics to sell to collectors. Leaphorn flies to New York to seek a clue from one such collector.

The trail leads him as well to a previous case and a bitter old man whose son Leaphorn identified as a multiple killer. The young man, a paranoid schizophrenic, is presumed drowned, but was he?

Crime series have a way of running down, the fleshings-out ever less able to conceal the bare bones formula. But Hillerman, it is admittedly a cliche to say, gets better all the while. “A Thief of Time” builds to a socko finish, with bow and arrow and helicopter metaphorically colliding among the tortured cliffs.

Compassion was central to Hillerman’s point of view from his first novel, the first of the Navajo mysteries, “The Blessing Way,” in 1970. But the feelings seem to run even deeper now: Leaphorn dealing with his private sorrow but dealing as well with a father’s grief over a son lost to madness if not to death.

Hillerman was born and reared in Oklahoma and attended an Indian school for the first eight grades. As he has said, Native American beliefs run deep into his own life, and he has studied them ever since. After a series of newspaper and wire-service jobs in Oklahoma and Texas, he joined the Sante Fe New Mexican and was finally its executive editor when, in 1963, he went back to school, as journalism professor, assistant to the president and student, at the University of New Mexico in Albuquerque.

His Joe Leaphorn is an individual with claims to being an archetype--an American Indian trying to straddle the old ways and the new, caught in a kind of limbo between mystical tradition and later rationality, between symbolic feathers and walkie-talkies. The two worlds are joined, as Hillerman demonstrates in the books, by an enduring family feeling that transcends all else, including material possessions.

By now, Hillerman’s sensitive handling of Indian ways and the Indian past, his summoning of the sights and sounds of the land and his understanding of the often uneasy and abrasive meeting of cultures have won him a place in American letters and not simply among crime writers.

But in less solemn terms, as a storytelling inventor of plots and generator of high suspense, he has no exact equal among the writers about crime either.

Like Elmore Leonard and other writers who worked for years to a small but steadily growing coterie of admirers before breaking out into wider attention, Hillerman now seems poised for the big acclaim. “A Thief of Time” begins with a 50,000 cloth print order--not Leonard country yet but impressive--heavy advertising and a 10-city tour for the author. It’s time.