A PSYCHOLOGICAL NOVEL of haunting quality, The Twyborn Affair is never more so than in the delicate encounter that a few days later leads Patrick White's protagonist, near the end, down a street of fire and blood. The scene is a park bench in London near a decaying church on the eve of the German Blitz.

"The women continued sitting side by side, till Eadie found the strength to rummage in her bag, and when she found the pencil she was looking for, to scribble on the prayer-book's fly-leaf . . . 'Are you my son Eddie?'"

The woman beside her writes a reply. "Eadie Twyborn read when the book was handed back, 'No, but I am your daughter Eadith . . .'

"Presently Eadie said, 'I am so glad. I've always wanted a daughter.' The searchlights had begun latticing the evening sky."

After 35 years of wandering through names and sexual roles (male, female, androgyne), the son who changes identities -- Eudoxia, Eddie, Eadith -- in Patrick White's novel finally is revealed to his dotty mother. She had suspected. She knew from her own choices that sex wears costumes and plays charades, exploits friendship and forgets love. Eadie Twyborn is only somewhat less a lesbian than her son Eddie is a homosexual.

We first see White's hero/heroine in St. Mayeul, France, in the spring of 1914, through the eyes of a pair of fat Australian aristocrats vacationing on the Riviera. The Golsons know Judge Twyborn and his cigar-smoking wife Eadie well. (The wives play at sex together.) They ruminate over the Twyborns' suffering: years ago their only son disappeared after engagement to a society girl.

Joanie Golson is a voyeur, and she begins to spy on a woman worthy of lust. Eudoxia, object of her desire, is the lissome mistress of 68-year-old Angelos Vatazes, a Greek nut who claims descent from Byzantine royalty and raves madly about glory, loss, and troubles in the toilet. Eudoxia's eyes signal memory in Joanie Golson, but too late. Soon after the Golsons make a comic visit to the couples' cottage, Vatazes and his mistress vanish.

We next see Eudoxia in the spring of 1920 as Lt. Eddie Twyborn, D.S.O., a demobbed army officer aboard a ship headed for Australia. Returning to his suffocating home, Eddie tangles moods with his parents and one day catches his mother and Joanie Golson in the drawingroom mirror, an "inchoate mass of flesh desperately gobbling at flesh." On manly impulse he joins an outback sheep ranch as a "jackeroo," snaring rabbits, sheering sheep and serving as gigolo to the owner's bored wife. With Marcia Lushington Eddie is "balanced again on the razor edge of motives, between truth and lies." She reminds him "somewhat of a raw scallop, or a heap of them, the smudged ivory flesh, the lips of a pale coral." Marcia protests his sexual diffidence: "I thought we could lose ourselves in each other." He replies that "finding myself is more to the point."

We lastly meet Eddie as Mrs. Eadith Trist in London a few years before World War II and shortly after she has established her simple, two-girl whorehouse. Mrs. Trist eventually creates the most fashionable brothel in Chelsea -- Bokhara rugs, ministers of state, and all known forms of depravity. Mrs. Trist leads a shadowy life and is "too disgusted with herself, and human beings in general, ever to want to dabble in sex again." Ironically she falls, quietly and painfully, in love with one of the brothel's sponsor-patrons, but consummation is forbidden.

The three narratives of White's novel take place years and distances apart. Only inference, imagination, and Eddie's memories connect them. Yet they cling together with the intense reality -- and counterbalancing romanticism -- that authentic literature always asserts. In a precis White's novel is incredible. In total it's as believable as a nervous breakdown: a dazzlingly handsome, emotionally fractured young/middle-aged man does live as man/woman in The Twyborn -- twice born? -- Affair.

Patrick White breaks down disbelief. His characters conduct their lives and animate their emotions with our own confusions. Plainly autobiographical, at least in part, this 11th novel by White comes in his 68th year. There may be something urgent about his extra-literary insights into homosexual behavior. But "love can never be conveyed except by the wrong gestures" and "anything wholly true -- certainly in friendships -- comes . . . from the woman in a man and the man in a woman" suggest his ambiguity. The essence of homosexuality in The Twyborn Affair is indecision, fear, flight.

Most homosexual fiction, like mose deliberately heterosexual fiction, is propaganda. Not The Twyborn Affair, which carries the literary grace implied by White's Nobel Prize. While White's achievement is in making Eddie Twyborn so credible he pleads for sympathy, White's limit is in making him comprehensible. Indeed, White's explanations for Eddie's bizarre preference limp back to conventional wisdom: butch mother, absent father, retreat into self. White gives us the condition of his character. One keeps looking through the extraordinary novel for his deepest source.