NOVELIST Robert Olen Butler's Vietnam is a surrealist cinema set under clouds of evil. This is his fourth novel, and he has been there before. His time is the collapse of the south in 1975, culminating in the fall of Saigon, an event which American television etched into the mind of a nation, and his action, the disintegration of the American war machine, grinding on while it dies.

In the midst of these horrible things, his hero, David, Army captain and CIA operative, is being court-martialed back in the States because of an irrational and heroic deed. David had released an important Vietcong suspect out of compassion (the man had been tortured to the edge of death and madness) and now the momentum of military justice has finally ground to its conclusion.

This would be rich enough a brew for most concocters of narrative, but Butler, whose previous novels have won lofty praise, is a writer obsessed with men's hidden motives, urges which lie so deep that they can erupt to defy the control, and even the understanding, of their characters.

So it is that David, careless of the court-martial he's caught in, conceives a conviction that he has a child, which he somehow knows is a son, back in Saigon, the fruit of a liaison with a well-off Vietnamese woman. The novel weaves its threads around the search for the mother and the son, a return to Saigon a few days before it falls, and a climactic discovery.

Butler's hero lives both in the present and the past and has two parallel lives -- the Vietnamese nightmare which will not fade from his mind, a kind of permanent post-traumatic disorder, and his American life, which he lives with a wife and a son who is born during the court-martial. The wife is a blank, or rather a line of continuo, a stock figure. Butler, a soldiers' writer, a writer about men, is curiously like Conrad in his understanding of the female principle but not its personification.

What he creates in David is a recognizable and infrequently explored modern character, the hero who is crippled by his desire to put things right, who runs afoul of "systems" and is destroyed (or at least disgraced) by them, but not before he is able, by lonely and misunderstood deeds, to accomplish his objectives. He may not even understand these objectives, but their force can only be called a moral imperative.

This is to say that Butler's novel aims at the highest themes of literature, the exploration of the human heart, the terrible loyalties of blood, the instinctive springs of honor. While the marketplace is full of writers of greater facility who have less to say, Butler's stark and simplified style, which snorts and gallops on in sentences as short as the lines left by some Anglo-Saxon bard, makes his clouded and complex message seem exalted, desolate, grand.

THIS STORY of a man's longing to repossess a lost son, who remained hidden to his mind until his other, Caucasian son breached some interior dam, could have been set anywhere in Vietnam. Butler chooses to place it against the backdrop of Saigon's final convulsion of fear, self-hate and blank despair as the triumphant Vietcong surround, bombard and penetrate the helpless city. It is an invocation as powerful as any written about that mordant event.

The problem of the primary plot, involving David's impulsive release of the Viet Cong officer years before, is less concrete and less dramatic. While an intelligence investigator, David becomes suddenly repulsed by the filthy business of extracting information by torture. The reason is precise: he ventures into one of the airless cells where the Vietcong suspects are kept before they are tortured, frequently to death. There, he sees a poorly hidden message scrawled in Vietnamese, apparently by a prisoner. "Hygiene is healthful," it reads.

David's imagination allows him to make an existential hero of the author of that obscure statement. "An image of the prisoner was instantly born in David; the detachment of the man's mind, his unassailable irony, his courage. There was no face yet, no form, but a sense of the man himself, very clear, clearer to David than any friend." David's is a conversion stronger and stranger than those of the born-again .

From that moment, the American officer's life is forever changed. The words on the walls of the wretched cell become the only things that make any sense of his military career. At the first remove, his liaison with the Vietnamese woman receives the same charge of importance, and at the second remove, the life of the child of that liaison becomes the only saving grace of his Vietnam war. He first finds and releases the Vietcong he thinks wrote the message; he then leaves his wife and newborn son to try to seek out his former lover and child under the feet of an advancing army. He has gone crazy to become sane again.

A wise editor once said that there are 99 ways to write a story, and only one of them is wrong. Butler has chosen his stiff, unadorned, purposefully choppy style. It is not flashy, it is not "smart" or amusing. His sentences are like short logs streaming past in a choked river; they evoke disruption, they evoke a pall of doubt and unease, as if something terrible were out of sight upsteam, laying waste the land. Here is the power of this young writer's message: to suggest insistently that Vietnam cannot be cured, healed, covered, or forgotten, but that it is out of control in our hearts.