BOSTON, Jan. 14— After dinner at a restaurant last September, a close friend says, Charles Stuart complained that he had noticed something about his pregnant wife, Carol, that he had never seen before, ''that she had the upper hand'' in their marriage.

As the friend, David F. MacLean, recalled last week, Mr. Stuart was upset that his wife had refused to get an abortion and he was worried that she would not go back to her job as a lawyer after giving birth, lowering the couple's income. Mr. Stuart then made a startling proposal, Mr. MacLean said. He asked for help in killing Carol Stuart.

This account by Mr. MacLean may be the closest anyone can get to the mind of Mr. Stuart, who the police now suspect shot and killed his wife and then seriously wounded himself in the stomach on Oct. 23 as part of an elaborate and tragic scheme. Mr. MacLean's account was given last week in an interview with WCVB-TV, and he is believed to have repeated it on Friday to a grand jury investigating the case.

At the time of the shootings, Mr. Stuart told the police that the couple had been attacked by a black gunman after they left a childbirth class at a nearby hospital. His story unleashed racial passions in Boston and touched off a wave of national sympathy for Mr. Stuart, his slain wife and their prematurely delivered son, Christopher, who died 17 days after the shooting. But on Jan. 4, 12 hours after his youngest brother, Matthew, told investigators he had taken part in the incident, Mr. Stuart apparently leaped to his death from the Tobin Bridge over the edge of Boston Harbor.

Much about the case remains uncertain. But friends, relatives and law-enforcement officials now say Mr. Stuart may have been consumed by his own rapid financial success. He was a man who had gone from being a short-order cook in a bar a decade ago, making $4 an hour, to the manager of a fur salon on Newbury Street, earning more than $100,000 last year.

It was a long journey from his hometown of Revere, a blue-collar community best known for its dog track and neighborhood bars, to the affluent environs of Newbury Street, with its fashionable boutiques and crowded restaurants in Boston's Back Bay. And it was a long passage from the vocational school where Mr. Stuart studied culinary arts to his job at the furrier Kakas & Sons, with a lawyer wife, a car phone and a slate-blue house in a comfortable suburb with a swimming pool and Jacuzzi.

But Charles Stuart, who turned 30 in December, seemed to hunger for more. Neighbors said he talked of opening a restaurant, and he attended a course last spring at the Boston Center for Adult Education, called ''Buying and Operating a Restaurant Successfully,'' an instructor says. Investigators say that for now their best guess is that he wanted to collect on several life insurance policies held by his wife, which are known to have amounted to at least $182,000.

'Not the Chuck I Knew'

But even his relatives are still not sure they understand how Mr. Stuart, a tall, handsome, affable man who had never been in trouble with the law before or displayed a flair for the imaginative, could have devised such a bizarre scheme.

''This was not the Chuck I knew; it must be another Chuck,'' said Stephen F. Reardon, a cousin and co-owner of Reardon's bar in Revere. ''It must have been a Chuck with a sick thing inside of him.''

Dr. Robert Coles, a psychiatrist at Harvard University and author of books on moral development, said that from what he has heard of the case he believes Mr. Stuart was an extreme example of a psychopath, an antisocial personality with little sense of remorse, a propensity to lie and often an ability to deceive others into believing his fantasies.

''In most psychopaths there is cruelty and callousness, but Stuart outdoes that,'' Dr. Coles said.

He said the case was not so much about Boston and its history of ethnic and racial animosity, as many people have suggested, as it is about Mr. Stuart's own personality and perhaps his family background. The Family A Dark Role, Even If Unwitting In fact, as lawyers for members of the Stuart family have acknowledged, Mr. Stuart's three brothers and two sisters, as well as their spouses and friends, either participated in part of the crime, wittingly or unwittingly, or learned about it at various points without telling the police.

A lawyer for Michael Stuart, a 27-year-old firefighter, said last week that Charles Stuart had asked Michael to help in killing Carol Stuart ''weeks before'' the Oct. 23 shooting. Michael refused, the lawyer said, but by Oct. 26 had been told that Charles's public account was not true by another brother, Matthew, 23.

John J. Perenyi, a lawyer for Matthew, has said that his client had driven into Boston by prearrangement with Charles Stuart to meet him near the hospital and picked up a silver, snub-nose .38-caliber revolver as well as Carol Stuart's jewelry and handbag. Matthew thought his brother was only planning a jewelry insurance scam, Mr. Perenyi said, although the police have said Charles Stuart had offered him $10,000 for his role. Matthew had been through a ''dry run'' with Charles a few days before, and there have been reports from neighbors that Matthew also participated in an aborted fake burglary at the Stuart house in Reading, where Charles may have intended to kill his wife and make it look like a robbery.

Both Michael and Matthew were pallbearers at Carol Stuart's funeral. When Matthew finally went to the police on Jan. 3, his lawyer said, ''There wasn't a lot of support in his family for him going to the authorities.''

Carl DiMaiti, Carol Stuart's brother, mused about the Stuart siblings in an interview with WLVI-TV last week. ''Can you believe that they came over to our house to comfort my parents?'' he asked. ''It is just mind-boggling that they could sit with us, or allow us to visit Chuck, to cry over him and pray for his recovery, knowing that Chuck was responsible for what happened to Carol.'' The Clues A Life Story, Embellished In hindsight, there were clues earlier in his life about Charles Stuart's capacity to embellish.

He told friends, and the story made its way into his resume and later into the Boston papers, that he had gone to Brown University on a football scholarship but had dropped out because of a knee injury and eventually graduated from Salem State College in Salem, Mass.

But a spokesman for Brown said a check of its records revealed that Mr. Stuart had never even applied to the school. An official at Salem State said Mr. Stuart had enrolled there in September 1979, but dropped out after two months.

Mr. Stuart may have wanted to obscure the memory that he actually went to Northeast Metropolitan Regional Vocational High School in Wakefield, north of Boston, a school that teaches trades like auto repair, cosmetology and pipe fitting and offers academic subjects in alternate weeks. By 10th grade, Charles Stuart had chosen culinary arts, spending every other week working full time in the school's kitchen and helping to run its restaurant, the Breakheart Inn.

Bill Lord, his instructor, remembers the teen-age Mr. Stuart as ''an excellent cook who expressed no interest in going to college.'' Mr. Lord said Mr. Stuart was ''a good kid.''

''I never ever once had to send him to the vice principal's office for misconduct, like you had to with a lot of kids,'' Mr. Lord said. 'He Was Very Happy'

Over the years, they kept in touch, and Mr. Lord said that last year Mr. Stuart had stopped by the school one day for lunch. ''He was very happy because he was making lots of money and thought he had very good prospects.''

The teen-age Charles Stuart was interested in sports, but contrary to his own account, he never played football. Instead, he played baseball and was ''an average fielder and a poor hitter,'' his former coach, Dennis Bisso, recalled. He also played basketball, and was a good shooter but rather slow, said Dave Barriss, his basketball coach.

Mr. Stuart was born on Dec. 18, 1959, the son of an insurance salesman and a part-time bartender who was ''a natural entertainer, with a new joke every day,'' recalled Stephen Reardon, his cousin. The family lived in a modest red Cape Cod-style house on a dead end street, and young Chuck and his brothers attended the Roman Catholic elementary school run by the Immaculate Conception Church nearby.

When he graduated from vocational school in 1977, Mr. Stuart got a job as a cook at a now-defunct Italian restaurant in Revere, the Driftwood. It was there that he met Carol DiMaiti, a Boston College student who was working as a waitress.

''He was very popular with the women, and she fell madly in love with him,'' said Rosemarie Bartolo, who also worked there at the time. But Carol's father, Giusto DiMaiti, who was the bartender in the Driftwood, ''didn't like him,'' Mrs. Bartolo said. She had been going out with a boy who was a college student and, like her, was an Italian-American, Mrs. Bartolo recalled.

Seen as Quiet and Reserved

Like many people who knew them, she said that where Carol was outgoing and ''talked about her problems pretty freely, Chuck was quiet and reserved, kind of introverted.''

In about 1981 Mr. Stuart gave up cooking and applied to Kakas & Sons, the fur store. He told his teacher, Mr. Lord, that ''he was having trouble with his legs, standing all day.''

Both Ted and Jay Kakas, co-owners of the furrier, refused requests for an interview. But in October, soon after the shooting, Ted Kakas told The Boston Globe, ''He was just an all-round terrific guy. I think I can say he was loved by all of our employees.'' The store was closed for Carol Stuart's funeral because everyone who worked with Chuck wanted to attend.

To all appearances, things were going well for Chuck and Carol. They got married in 1985, bought a house in Reading, a much more affluent town than Revere, and after Carol became pregnant last year, they began buying baby clothes and furniture. Carol was due in December.

''Carol was so happy and sweet,'' said her hairdresser, Mali Sheikhi, in Newton, near the publishing company where Carol worked. ''I was always telling her, 'You never seem to have any problems.' ''

Complaints by His Wife

It was only after Mr. Stuart's apparent suicide 10 days ago that another side surfaced. Maureen Vajdic, the Stuarts' neighbor, remembered that Carol had begun complaining last summer, after she got pregnant, that Charles was going out on Friday nights by himself and staying out late.

At the time, Mr. Stuart was becoming interested in a 22-year-old woman who worked in the Kakas shop, Deborah Allen. Friends say Ms. Allen, a graduate of Brown University, is strikingly attractive. They went out for meals together, and last fall, before the shooting, she took him on a tour of her prep school. Mr. Stuart gave her a pair of sneakers and a sweatshirt.

After the shooting, Ms. Allen began calling him regularly in Boston City Hospital, where he lay recovering from his stomach wound for six weeks. In a statement made public by her lawyer, Thomas E. Dwyer, Ms. Allen said she called at Mr. Stuart's request and charged the calls to his telephone credit card. But when Mr. Stuart tried to turn their relationship into something more intimate after he was released from the hospital in December, Ms. Allen broke it off, Mr. Dwyer said. If Mr. Stuart's interest in her so soon after his wife's death raised any suspicion, she never told anyone. The Tale The Final Days Of Charles Stuart It is not known how Mr. Stuart got the idea that he could successfully deflect attention from himself by saying the couple was attacked by a black gunman. But there had been a series of drug-related shootings last September and October in the city's black neighborhoods. ''Chuck and I had talked about the number of shootings that had gone on there,'' said Peter Jaworski, an employee at the fur store.

Mr. Stuart's upbringing in Revere may also have played a part. ''Don't discount the way people think here,'' said a customer at Reardon's bar. ''Racism is a fact, good or bad. We divide people up into groups, and you will notice no blacks live in Revere.''

But it was Mr. Stuart's coolness after the shooting that amazed even his own relatives. Patrick Reardon, another cousin, said he was in the hospital room with Mr. Stuart when the police first questioned him about the shooting, two days after it occurred. ''I was boasting to friends about how good his recall was,'' Mr. Reardon said.

Repeated Details of Shooting

''He went through the whole thing. They asked him several times, and he repeated it every time,'' he said. ''He didn't seem to get annoyed. The way Chuckie had described the assailant led you to believe that it was real. He went as far as to describe a stripe in the sleeve of the running suit and how the gunman reached into the inside of his zipper jacket for the gun, turned and faced him.''

Nor did Mr. Stuart apparently have trouble composing a message that was read by a friend, Brian Parsons, at Carol's funeral. ''Good night sweet wife, my love. God has called you to his side,'' he wrote. Referring to her killer, the message continued, ''In our souls we must forgive this sinner because He would too.''

Within two weeks of being released from the hospital early last month, Mr. Stuart was buying women's jewelry, first a $999 pair of diamond solitaire earrings, later a $250 14-karat gold brooch. ''It struck me as funny, because why would he be shopping,'' said John White, who sold him the brooch. ''He didn't express any grief at all.'' The police have speculated that the jewelry was intended for Ms. Allen, but she has denied receiving any items from Mr. Stuart.

Mr. Stuart told his relatives he was going to return to his house in Reading. Socially, if not emotionally, he had moved from Revere. He had stopped playing in a Thursday night basketball league there several months before his wife's death, and before that had stopped having drinks with his teammates at the Speakeasy pub after games, friends say.

'One Less Traveled By'

It was as if Mr. Stuart was living out the poem by Robert Frost that graced his high school yearbook - ''The Road Not Taken.'' Two roads diverged in a wood, and I -I took the one less traveled by, And that has made all the difference.

On the last night of his life, with the police looking for him, Mr. Stuart checked into the Sheraton Tara motel in Braintree. He requested a wake-up call for 4:30 A.M. Then he drove into Boston, stopped his car on the bottom level of the Tobin Bridge, and turned on the hazard lights on the $22,000 Nissan Maxima he had bought only two days before. Leaving a note on the front seat that said he could not bear the charges against him but did not make clear his own role, he got out and propped up the hood.

When the police found his car at a few minutes before 7, they were not sure, until they found his submerged body, that this was not another hoax.

photo: Charles Stuart, center, who went from short-order cook to manager of a posh fur salon, in a 1978 yearbook picture of his cooking class. A friend of Mr. Stuart says he wanted to kill his pregnant wife because he feared she would endanger his life style by refusing to return to work.; Matthew Stuart, who implicated his brother Charles in the killing of Charles's wife, Carol.; Carol Stuart, who, a friend says, angered her husband, Charles, by refusing to have an abortion. (AP) (pg. A13)