WILLIAM TREVOR, like many of the characters in his novels and stories, is something of a con artist. The boring opening to his new novel, Other People's Worlds, is a setup. We are introduced to the world of Swan House where a 47-year-old widow named Julia Ferndale lives in co bwf tranquil "doziness" with Mrs. Anstey, her 81-year-old mother. Julia is a few weeks away from her wedding to 33-year-old Francis Tyte, a handsome and charming man, chivalrous and urbane and, seemingly, one more stitch in "the lace-work quality of their life." The middle-class "Englishness of everything" is soporific. The two women, part of a respectable old "family down on its luck," are referred to as "inmates," and one certainly feels their little world resembles a comfortable prison. That Trevor is willing to lull us for 20 or so pages, only to jolt us back awake by revealing that Francis Tyte, the intended groom, is in fact an impostor with the sinister mission of violating the peaceful contentment of Swan House, is the first of Trevor's tricks in this novel, one of many masterful strokes by which he shifts our perceptions.

Other People's Worlds is "an English tragedy" about victims and predators with Francis Tyte (who is, among other things, a minor-league actor) in the starring role. Besides Julia Ferndale, the cast of Francis' complicated life includes: 40-year-old Dorrie Smith, a lower-class, shoe-store clerk and mother of Francis' illegitimate 12-year-old daughter Joy; his abandoned wife Lucille, a dressmaker in Folkestone who is 30 years his senior; his parents, aged residents of the Sundown Home; the debt-collector, a one-time boarder in his parents' house whose seduction of the 11-year-old Francis introduced the boy to treachery and evil; the men he meets during his occasional stints as a male prostitute; and the actual cast of a television show (in which Francis has a bit part) on the story of Constance Kent, an adolescent girl accused in a "Victorian murder case."

Frankie (as Dorrie Smith calls him) is the center of attention in the novel, but Julia Ferndale is its emotional center. Julia is an intelligent, attractive woman with a sincere belief in God and with a character so trusting that she makes an "easy target" for Frankie, as have so many others in his many lives. He lies to her habitually, telling her that his parents died in a train crash, that he has never married, and that, like her, he is a Roman Catholic. Vulnerable, compassionate, Julia believes it all until the first day of their honeymoon in Italy when Frankie takes her jewels and abandons her, leaving Julia to face her shattered illusions, her new doubt in God, and her growing sense of the world's malevolence. Julia winds up entangled in the lives of the other people Frankie has left behind, and the way she comes to terms with her victimization and crisis of faith is at the heart of Trevor's book.

Julia's "childhood vision" of God as "greyly bearded and venerable in a tropical garden" proves too simplistic a figure for a world whose multidimensional reality requires a more complex and ambiguous concept of God. After Frankie has "smashed . . . to pieces" her illusions, Julia becomes more and more aware of the world's evil: missionaries are clubbed to death in Africa, "a legless man in Arizona was tormented by teenagers until he died. In Birmingham a husband killed his wife with a knife because she wouldn't cook his bacon right. Bombs explode everywhere." Her "bearded cloudy God" becomes "a wisp of nothing" in the face of such pointless evil.

Trevor's ironic sense of reality involves a constant challenge to, and mockery of, traditional concepts of God. Frankie's daughter notices "a black message" sprayed on a fence, an assertion "that Jesus Christ was alive and well. Working, it added, on a less ambitious project." This scaled-down Jesus seems much more qualified to preside over Trevor's fictional world. Taking this contemporary theology one step further, Trevor suggests parallels between Jesus and Frankie Tyte. He may be a liar who spreads "disease all around him," a scoundrel who uses people for his own gain, but Frankie is also "made for suffering." Living in a world of his own "make-belief," Frankie becomes a creator, a master of "ersatz existence," a man committed to his own perverse notions of love and forgiveness. And, significantly, he is 33 years old and the father of Joy.

When the cast of the television show debates the ambiguous facts of the Constance Kent murder case, they mirror our own uncertainty in responding to the ambiguous "facts" of Other People's Worlds. This is a novel "with truth and lies insidiously mixed and an outcome full of other people's pain." "It's difficult unravelling it," says Dorrie at one point. And towards the novel's end, Julia explains that "it was hard to establish just what was what."

William Trevor is an Irish-born writer, now living in England, who has published 11 novels and story collections in this country. Other People's Worlds seems certain to enlarge his American audience. On one level, this new novel is an old-fashioned, very readable, Gothic tale about the dialectic between good and evil, truth and illusion, innocence and guilt. Yet it is also a thoroughly contemporary work, not only in its details (this is an England of "Pizzaland" and television addiction), but in the ways it touches on our most up-to-date fears, most especially the fear of being vulnerable and compassionate in a predatory, violent world.

Trevor's prose seems careful, delicate, almost cautious at times. He builds his narrative by setting everything up, then knocking it down: the repeated use of facades and faces (and, finally, of demolition) in OtherPeople's Worlds gives this technique a metaphorical scaffold. But he is never too careful, and it would be a distortion to reduce his work to formulas on how his self-admitted "obsessions" all add up in the end.

It would also be a distortion to leave the impression that Trevor's novel is a bleak, pessimistic work. Julia Ferndale, a sane, sympathetic person caught up in what often seems to be a world of comic-book horror, does not so much surrender her innocence as her naivete. She holds on to her best qualities -- her character, her trust in people -- while qualifying them with a deeper sense of life's darker realities. Her spiritual survival is a source of hope, as the novel's last words suggest: "In spring there were mornings of sunshine."