THE OLD GRINGO. By Carlos Fuentes. Translated from the Spanish by Margaret Sayers Peden and the Author. Farrar, Straus and Giroux. 199 pp. $14.95.

THE MEXICAN NOVELIST, diplomat and political thinker, Carlos Fuentes, is a man of parts with many roles. The versatility which is the hallmark of his excellence applies to him as a fiction-writer, too. There is Fuentes the discreet implier, concerned with special and not always definable states of mind, as in Aura and Distant Relations. There is Fuentes the voluminous, wide-handed visionary, for whom nothing is too small, too big, to go into his homage to the planet, Terra Nostra. There is the severely moving Fuentes of The Death of Artemio Cruz, who masters the forlorn, the poignant, with impetuous vivacity. There is the Fuentes whose work in progress happens to be told by a fetus, and now there is the Fuentes of The Old Gringo, a cleverly conceived and crisply rendered book about Ambrose Bierce's mysterious last days, as an old man, in the Mexico of 1914.

The book's premise is that Bierce went to Mexico to die, in the army of Pancho Villa, because death is what Mexico is good at. It would be easier to explore this premise if Fuentes had come closer to Bierce's most hidden motives, but he backs off, only occasionally allowing Bierce to speak out, or dream forth, in his own words, in an idiom different from that of the novel's narrator: "This handiwork of man and beast, this humble, unheroic Prometheus, comes praying, yes, imploring everything for the boon of oblivion." The reader has to guess, wondering if indeed the old gringo saw a Mexican death as a fitting punctuation mark because death in Mexico, as distinct from death anywhere else, is more imposing, satisfying, incongruous or whatever.

After all, the author of "An Occurrence at Owl Creek Bridge" had a vested interest in death, its protocols and mannerisms. Shot, Fuentes imagines, in the back by a capricious junior general of Villa's, after making a solo horseback charge of indelible, reckless bravery, and after encountering too late for anything to come of it the exquisite and chaste Harriet Winslow of Washington, D.C., Bierce suffers a death every bit as enigmatic as his initial decision to go south of the border. Did Arroyo the general shoot him for being too brave, in other words for setting too high a standard; or for burning Arroyo's box of private papers? Take your choice. Or, better, shelve the question as if the novel were a movie (which it is going to be). Eye the events and decipher them as best you can in the absence of narrative help. I am not sure we aren't dealing here with an acte gratuit much as we find it in Andr,e Gide. At any rate, Bierce wanted his death, and gotit, so for him the causation could hardly have mattered.

To some extent, then, this general Arroyo is a contraption, but contraptions fit well into Fuentes' highly schematic book, fraught with echoes, parallels, and doubles, almost like an enfolded rose. To both Harriet and Arroyo, the old gringo is a father figure. She has lost her father, at first thought killed in the war, but revealed to have run out on his family. Arroyo is the unacknowleged son of a grandee. In the end, Villa, himself a father figure to Arroyo, has Arroyo shot for shooting Bierce, but not before he has him dig up the old gringo's corpse for "execution" from in front by firing squad, to keep up appearances. There are other such patterns and their interaction, like something underwater as you sail through the clear prose element above, imperils and thickens the action, turning everything that looks straightforward into something indisputably richer and stranger. Fuentes understands how the mind, especially in his myth-rich native land, modifies whatever it attends to, and in this case he allows room for the accomplice- reader to become part of the sea-change itself.

What looks, at first, like an almost allegorical tale becomes something much less obvious, less fathomable. Old gringo, young gringa, young general, older general, begin to overlap more than they don't, and in a weird way their roles drop away from them until each -- Bierce, Winslow, Arroyo, Villa -- begins to get lost in the others, not on the level of character, but in a hortatory ballet, staged with phantoms in the neutral desert.

Looking back on it all, Harriet Winslow can hardly credit what she lived through, remembering best her mental affair with the old gringo, her intense physical one with Arroyo. She has discovered contingency, what Henry James called "the insolence of accident." She cannot separate the inevitable from a whole series, a concatenation, of flukes, which has nonetheless defined her forever. A traumatized survivor, she inherits the theme "I cannot take it all in such a short time," and you wonder if, without realizing it, it is history she's talking about. Mantegna's Christ invades her mind, obsesses it, not least because she cannot link the old gringo as she knew him to the Ambrose Bierce who wrote the books. The man is dead before his name comes to life for her. On she goes, rehearing and rehearsing the monologues of ancient Mexico. The monologues seem almost as ancient as Mexico itself, although the events underpinning them were recent.

It's a haunting novel, easier to focus on with the second reading, and -- although a blaze of fierce action -- a book of interacting levels, one of which is contemplative: where the reader begins and ends, pondering the enigma of Ambrose Bierce, who became as baffling as Mexico in order to die at its visionaries' hands. The translation has a harsh sunlight in it.