IMAGINING ARGENTINA by Lawrence Thornton Doubleday. 214 pp. $16.95

OF ALL THE cruel tactics the South American military dictatorships employed in their recent wars on the enemies they discerned among their own people, none is quite so cruel as "disappearing" prisoners. Several regimes did it, but only the Argentine generals made it routine. An official inquiry, after their fall from power, reported 8,900 documented cases of people picked up by Argentine troops and police and never heard from again.

The victims were torn from their families at night or abducted in broad daylight on crowded city streets, such was the impunity with which the secret police moved. Requests for information would be met with the authorities' bland denial that they knew anything about the case. Distraught spouses would be told by a smirking officer that the missing person probably had run away with a lover, parents that their children had gone underground to join the "subversives."

The prisoners, in most cases, were tortured and violated beyond belief. Eventually, a bullet would end the suffering and the bodies were then buried in mass graves or dropped into the river or the sea. Beyond the horror was vindictiveness. The relatives were to be tortured with continuing uncertainty, denied the healing knowledge of a final resting place, of ritual and farewell.

Many of the bereaved refused to be paralyzed by the uncertainty. They insisted that, until they were provided clear evidence to the contrary, the person they had lost was still alive somewhere. They never stopped demanding information, they demonstrated in front of government buildings (and some of them also disappeared as a result), and they told their stories to anyone who would listen. I remember poor women in Chile and prominent lawyers and businessmen in Argentina telling of their stolen sons and daughters and each time, as they recounted the fragments of a young life, the few searing moments of the arrest, the missing person came alive, was there in the room.

What is so impressive about Lawrence Thornton's Imagining Argentina is that he grasped all that, and especially the power of those moments of story-telling, from a 20-minute television documentary about the mothers of disappeared prisoners in Argentina, a country he'd never visited. When the program was over, he sat down at his desk. A half-hour later, he had his central character, Carlos Rueda, who "thinks he has magic and can cure things with a story."

Rueda works as director of a children's theatre. Cecilia, his wife, is an outspoken journalist. When plainclothes men in a green Falcon abduct her from home, Rueda discovers the many other people around him who have also lost a relative. Listening to their stories, he makes a further discovery, that a word or an image "would link the speaker's pain to his imagination." When that happens, Rueda can complete the story. He can imagine the prisoners and describe their fate, in all its terrible detail. And sometimes, miraculously, he can carry the story into the future and imagine an escape that then takes place.

From the beginning, Rueda recognizes that his power is a gift. He also senses, as he tells the retired journalist who is the novel's narrator, that "I will lose the gift if I spend it only on myself." He cannot try to save Cecilia by imagining her escape until he has shared the power of his imagination with others. And so begin the weekly "seances" in Rueda's garden at which the suffering of Argentina's disappeared is recited. Thornton wisely chose for those recitals the unadorned and unblinking style that many human rights reports have adopted as the most effective way to describe evil.

Even more wisely, he lifted his novel above the level of denunciation by placing that material in the framework of a dramatic struggle, Rueda's imagination against the military's brute force, the courage of those who resisted and protested against the fear that caused the majority to avert its eyes from what was happening. Rueda is not simply a guru to the Mothers of the Disappeared, but a brave and passionate man who like them keeps fighting for information and for the right to speak out. Using his gift, he exposes a government infiltrator among the protestors and a cowardly professor who informs on non-conformist students. Rueda's theatre is closed down; government goons almost crush his skull and abduct his daughter. Because of his "gift," he can see her agony. Despite all that, he clings to his faith that imagination will eventually prevail over terror.

At one moment, almost crazed with the need for revenge, Rueda tracks Guzman, the general who masterminds the disappearances, and has him in the gunsights of his rifle. Yet he stays his finger, realizing that if he kills Guzman, he himself will be killed, or have to flee into exile. In either case, his voice would be stilled, and he believes his stories are more dangerous to the generals than his rifle.

When he confronts Guzman in his office in the presidential palace, the struggle seems equally joined, and it is Rueda who pronounces the regime's epitaph. "You made the terrible mistake of not knowing what to kill," he tells the puzzled general. "It is imagination."

THE NOVEL IS about Rueda's imagination, but it is also a testimony to Thornton's. In a time when much North American fiction is contained by a crabbed realism, Thornton takes for his material one of the bleaker recent instances of human cruelty, sees in it the enduring nobility of the human spirit, and imagines a book that celebrates that spirit. Like some of the Latin American writers whom he says influenced him, he keeps alive throughout the tension between history's brutal reality and the magic of which man is capable. And then history cooperated to give him the setting for a fully satisfying ending.

Seldom is history so compliant with poetic justice, but in the case of Argentina, Rueda's epitaph was prophetic. More and more Argentines joined the protests; the generals' power ebbed. Desperate, they gambled against the British Navy in the Malvinas war, and lost. Thornton ends his novel with Rueda, finally able to complete Cecilia's devastating story, in the courtroom when the dishonored generals are sentenced, under the due process they denied their victims, to long prison terms.

Patrick Breslin, the author of "Interventions," a novel set in Chile.