Sanctified Madness : THE SHRINE AT ALTAMIRA, <i> By John L’Heureux (Viking: $19; 261 pp.)</i>

As the prologue of John L’Heureux’s “The Shrine at Altamira” warns, “We hear stories like this on television but we do not look, and when they turn up in newspapers, we glance away, because we know there are crazy people and people who are mad with love, but we refuse to know any more than that.” Fortunately, L’Heureux has never been a writer to turn away from stories others fear. Perhaps his most ambitious novel, “The Shrine at Altamira,” is also his most successful; his sixth in a career that has examined the hardest questions of faith and love, it is certainly the most affecting.

When Maria Alvarez sees Russell Whitaker at a school dance, she wants him as much as she wants to escape her life in the barrio. Maria will not be satisfied by Russell’s words of love, by his name or even his seed, but only by evidence that he wants her more than she wants him; she needs to see she has driven him crazy with love. At the end of this tragic and astonishingly redemptive novel, she will have been given more proof than she can bear.

As soon as Maria has snared Russell, she begins to tease him: She tells him she doesn’t love him, cannot marry him. The effect of this torment is more profound than she guesses; once an abused child, Russell suffers her cruelties acutely, and unwittingly the girl has set the tinder for a conflagration that will destroy all she cares for.

Maria marries Russell, takes his Anglo surname and bears him a son, and then divorces him. After a period of alcoholic drifting, Russell returns to insist on his right to visit their son, John, but it is Maria who draws him. Spying on his ex-wife the night before he comes to pick up John for an overnight trip, Russell catches Maria in the arms of another man. Father and son never reach their amusement-park destination, because Russell drugs John and sets him on fire in a motel room; thus does Maria receive what she desired: proof that she has driven Russell mad with love.

John survives to endure a grueling series of reconstructive operations on his face. His surgeon is Dr. Clark, a man whose work is a vocation in the religious sense of the word, “saving what could be saved, repairing what could be repaired.” Unable to reconcile himself to blatant evidence of evil, Clark confronts Russell in prison; he wants to discover that the boy’s father is a monster, because if he is not “God’s terrible mistake . . . What hope was there for any of us?” But the man Clark sees is merely human, someone who has sinned grievously and wants only to be punished.

After the fire, John replaces Maria in Russell’s obsessive longing, and father and son are destined for a resolution that cannot include any other character. The boy dreams of union with his father; when he meets him for the first time after Russell is paroled, John realizes that the man who burned him is the only person who can look at his gruesomely disfigured face without flinching.

In his deepening crisis of faith, Clark seeks advice from an old priest who tells him that “What makes life so horrible is that even our salvation never comes in the form we would have chosen.” So it will be with Russell and John: Their salvation, shocking and inevitable, cannot comfort Maria or anyone who witnesses the final consummation of their mutual passion. Around the central drama of sinner and sinned against, L’Heureux, in brilliantly economical strokes, sketches the range of human faith, from Maria’s mother, whose belief accepts all, to Clark’s psychiatrist, who says God is no more than an invention of the weak-hearted.

Ultimately, only the old priest can explain a story such as this: “God sanctifies us--he makes us saints--in his own way. Not in our way. It never looks like sanctity to us. It looks like madness, or failure, or even sin.” John and Russell are so sanctified, and readers of this luminous novel will marvel that John L’Heureux has somehow conspired to redeem the unforgivable.