In the Gunsights of the Devil : The difference between a man and a monster is an absence in the soul : FELICIA’S JOURNEY, <i> By William Trevor (Viking: $21.95; 213 pp.)</i>

The story has an awful classic simplicity: a duel between the meek and the monster, and guess who wins?

Felicia, a simple, stumbling Irish country girl, gets caught in the gunsights of the devil, in the person of the catering manager of a factory in the English Midlands. It is a close-run thing, at times, but in just about every folk tale I can think of it is the devil who ends up up-ended.

William Trevor, who is good at a great deal, is particularly good with the meek; and most particularly with the rural Irish meek. He finds the passion in them, and he finds the ruses they devise to preserve not only their lives but something more: a kind of honor. In Felicia, who comes to England to look for the lover who has jilted her, he has a character that no one can write better. He has written it several times, in fact, and in its double melody--the obbligato of humility and a ground-bass of anarchy underneath--there is a practiced quality. Still, there are new notes to hear, some quite lovely.

With monsters, he is less practiced but also less skilled. True, he can do splendid bullies, tricksters and arrogant bastards; but in each case he builds on their humanity and warps it just enough. His villains have their vitality. You might catch yourself growing fond of them. Like the green bay tree they flourish; there is sap there, and certainly life.

A monster, on the other hand, is a kind of void. As the Church Fathers put it, evil is an absence. A writer can portray a man with a hole--an absence--in him, but a writer needs to be a special kind of metaphysician like Graham Greene, or else a pulp-horror master like Stephen King, to make the hole the character.

Hilditch, the pulpy, tiny-handed, gentle-mannered sex-murderer in “Felicia’s Journey,” is not a character but a trap. Trevor rigs him adeptly, and gives him any number of creepy adornments. His mother had compulsive sex with every man she met--a policeman, a door-to-door salesman, a fellow-passenger in a train going through a long tunnel with child-Hilditch watching--and finally with the boy himself.

An explanation does not make a character, though, and neither do all the shuddery strokes with which Hilditch is drawn. He lives alone in a Victorian house with eight bedrooms and masses of mahogany furniture. He is a compulsive eater, continually shopping for food, preparing large breakfasts--sausages and bacon--and planning what he will cook next. That makes him a great success at the factory where he is highly esteemed for the energy and devotion he musters to feed the workers. From time to time he muses on what he calls his Memory Lane: Jakki, Sharon, Beth, Elsie and Gayle, all of whom, as he words it, “parted from him.”

Along comes Felicia, who took money from under her great-grandmother’s mattress, packed some clothes in carrier bags, crossed the dismal gray Irish Sea on a stinking ferry, was copiously seasick--Trevor’s seasickness is not a product of the weather, it is the weather, or at least the soul’s weather--and arrived in the bleak town where, she believes, her Johnny works in a lawn-mower factory.

Trevor goes back and forth between Felicia and Hilditch as they converge and, eventually, “part.” Hers is the glaringly conventional story of the plain village girl who meets a handsome young man at a wedding and is romanced, impregnated and abandoned. Johnny is over from England for 10 days; when he leaves he forgets somehow to give Felicia his address. Stubbornly she tries to trace him, by vague and inaccurate clues, to the little town north of Birmingham.

Trudging from one factory to another, she is hailed from a car by a pudgy, gentle-mannered, middle-aged man. He directs her to the main factory district; later, encountering her again, he suggests a lodging house. On a third encounter he advises her to try another town, 20 miles away. He “happens” to be near the bus station when she returns from a fruitless trip; he makes up a story about a dying wife whom he must visit, and gives her a lift to still another town.

The spider spins a web of disinterested helpfulness; Felicia, whose diligent search exhausts her spirits and her resources--Hilditch accelerates the exhaustion by filching her money--flees him at one point but eventually takes refuge in his Victorian pile. There the “parting” takes place.

What the parting consists of is not immediately revealed. As Hilditch’s thoughts play out, what was at first only suggested becomes increasingly certain. He had picked up a series of women, waifs like Felicia, tried to hold them in his care, and killed them when they broke away. The final scene between Hilditch and Felicia is written in such a way that, for a while, we do not know whether he has killed her too.

Trevor creates an atmosphere of cloying nightmare around his monster. He uses a particularly effective device: although we see things alternately through Felicia and through Hilditch when they are apart, the viewpoint is entirely Hilditch’s when they are together. Our vision is skewed in his fish-eye; it is almost as if he had trapped us along with Felicia.

Certainly there is suspense as the story plays out. Yet it is suspense of a peculiarly abstract kind. We wonder, not what the characters will do, but what the author will do. Hilditch is not enough of a character to generate a moral or significant action; he is a device through which the author acts.

It is Felicia upon whom he acts, and she, indeed, is a real personage. Beneath her victim state, Trevor has planted hints of something else. There are sparks of exhilarating ruthlessness when she steals her great grandmother’s money, snatches an address from Johnny’s mother and, in a comically touching scene, methodically interrogates everyone she meets in one of the towns she visits. Most of all, there is a passage in which she moves beyond her quest to pursue an image of freedom that Trevor sketches in a fashion somewhere between realism and dream.

Too often, though, what is alive in Felicia is only hinted at. Most of the time it is overshadowed by the voice of Hilditch, the monster-contraption. It is almost as if Frankenstein’s creature were to recount the life of Mary Shelley.