Nobody seems to know what really happened during the afternoon hours of Nov. 7, 1975, on the grounds of the Southside Virginia estate. If there was the sharp crack of gunfire, nobody seems to have heard it.

But by 5 a.m. two days later, with her eminent father by her side, Alexandra "Sasha" Bruce gave up the last vital signs of her 29 years of life. Gunshot wound. Right temperal lobe near the ear. And within several days, the official ruling. Suicde.

If that was the case, her father career diplomat David K. E. Bruce, never believed it, according to family friends. And the investigation he began before his death last December at 79 has reopened the case, making headlines with four indictments returned since July by a Charlotte County, Va., grand jury.

The charges: murder, bigamy, and embezzlement and theft of thousands of dollars worth of silver, antiques and art from Staunton Hill, the Bruce family estate near Brookneal, Va.

The suspect: Marios Michaelides, 33, the Greek national who married Alexandra Bruce in a civil ceremony only three months before her death.

Michaelides now lives in Athens, Greece, where he is exempt from extradition under a teaty between Greece and the United States, because he is a Greek national. Under Greek law, he might be prosecuted in Athens, or might return to Virginia to face the charges under conditions he proposed last week.

Those conditions are that his trial be moved from Charlotte County, where he says the Bruces have undue influence, and that he and the Bruce family members who have made statements against him be given lie detector tests.

The lie detector issue drew attention yesterday when it was reported in the Washington Star that Alexandria's mother, Evangeline Bell Bruce, said she and her two sons would take plygraph tests if it would help the case.

Last night, Robin Young, Mrs. Bruce's private secretary, flatly denied that Mrs. Bruce had made the offer. "She definitely has not made any statement to the press, and she has no idea where it came from," Mrs. Young said.

Star reporter Duncan Spencer who wrote the story, said he had talked to Evangeline Bruce directly by telephone last Saturday. He said Mrs. Bruce made her statement about the possibility of a lie detector test in the course of that conversation, and reaffirmed it before the conversation ended.

Meanwhile, other twists came to light in the already tangled mystery:

According to sources close to the investigation, the gun that fired the fatal shot belonged to Michaelides;

No spent cartridge was ever found at the site where shsha Bruce's body lay, the same sources said

Telephone records show a number of calls were made in the days before Bruce's death from Staunton Hill to Tennessee, where Michaelides' first wife was living;

Sasha Bruce had sold her share of Staunton Hill to one of her brothers in early 1975, but the deed was not filed with the county until two months after her death - one month after Michaelides has renounced any legal claim to her estate.

Sasha Bruce: sensitive, rebellious, involved, beautiful, her friends say, and a poor judge of men. High-honors graduate of Radcliffe, 1969, after taking a year off to do social work and travel. A child of wealth and breeding. But enigmatic.

"She could be very, very gay, but she could be very, very despondent," said a friend who knew her well in college.

"She was destined to be a legend," said another college friend. "She was a legend at Radcliffe. There was an aura to her, but there was also something very vague."

And there were the romantic problems. "She had a sort of lousy taste in men," another friend recalls.

Whatever her taste, Marios Michaelides was not the first Greek in her love life. Michaelides was preceded by Greek-born Anton Von Kassel, a London art dealer whom Sasha Bruce met while living in Europe.

After Radcliffe and a year of dividing herself between social work and art, Sasha Bruce had gone to London to join her father and mother, the former Evangeline Bell. By late 1971, she had decided to live with Anton, and began another of the drifts away from her old friends that was becoming characteristic. She even received her mail under a pseudonym in London.

She opened an art gallery next door to von Kassel's. Von Kassel, meanwhile, drove a Rolls-Royce and a Range Rover, and he and Sasha, her friends said, lived expensively reportedly at Sasha's expense. Friends didn't question. "She was, after all, a very private person," one says. "You didn't intrude."

It was at this point that rips began to appear in the family fabric. Evangeline Bruce, Sasha wrote to a friend in mid-1972, was not happy with the direction Sasha's life was taking. "Her mother and Sasha always had a cool, distant relationship," a family acquaintance recalled.

Family relations appeared to smooth out as the affair with von Kassel trickled to an end in 1974. By April of that year, Sasha was on her way back to the United States, headed for Staunton Hill Farm.

"Nobody knew about Marios at the time," a friend recalls. Even today, few people do.

Michaelides, 33, had met Mary Lewis of Maryville, Tenn, about 1971 in Athens. They were married in St. George's Greek Orthodox Church in Knoxville, Tenn, a year later in a traditional Greek ceremony.

Mary stayed in Greece for a while but eventually returned to live with her parents. Marios paid visits to Tennessee and by late 1975, one thing was clear. She was proudly carrying the first child of her marriage.

Meanwhile, sometime in 1973 or 1974, Michaelides had met Sasha Bruce in London, while her relationship with von Kassel was crumbling. He told her she had to begin a new life, one of her closer friends says, and that she had to "cleanse" herself. "He wanted her to isolate herself from all of her friends, from all of her family," the friend recalls.

He encodraged her to go to Staunton Hill.

Staunton Hill and everything in it by then had been transfered by David and Evangeline Bruce to their three children, Sasha, David S. and Nicholas C. The horse was packed with family heirlooms and with David K. E. Bruce's priceless book collection.

During the spring of 1974, Michaelides paid one of his first visits to the estate. A family friend now says Michaelides kept Sasha Bruce in his company as much as possible and acted distrustful. The friend felt unwelcome and never returned.

Few of Sasha's friends ever saw her after that. Those who did say Michaelides resented them, and increasingly, built a barrier around Sasha Bruce.

Sasha Bruce, meanwhile, continued to lavish more than her attention on Michaelides. She and her brothers, friends say, gave him family heirlooms to sell and to keep - "almost as if they were giving away the farm," said one friend.

Finally, on Aug. 8, 1975, the couple was married in a civil ceremony by Edwin Hoy, then Charlotte County clerk of courts. Hoy recalls that Michaelides mentioned he was divorced, but says he doesn't remember the first wife ever being discussed. "I don't think she was ever mentioned," he says.

The isolation continued. People became concerned. Sasha's godmother and a cousin, on a trip south, finally called her to ask if she could visit for a weekend. Sasha said yes, and the date was set. It was to begin Friday, Nov. 7.

Sasha appears to have been looking forward to her godmother's visit. The morning of Nov. 7, she began work on a special dessert for dinner. She had the silver with the family crest polished and good wine brought out.

But some time between 3:30 and 4 o'clock that afternoon, Michaelides ran excitedly to one of the estate's farmhouses to fetch a Staunton Hill staff member who went with him to a site near the pool. There, under a tree, lay Sasha Bruce, dying.

Sasha's weekend guests arrived shortly before the ambulance, and went with it to Lynchburg General Hospital, 50 miles away where they called her parents. Sasha Bruce died there 36 hours later without regaining consciousness.

There are many questions about that day, but neither the state police nor Commonwealth's Attorney Edwin B. Baker, nor Downey Rice, the Senate investigator-turned-lawyer, whom David Bruce hired to investigate his daughter's death, will answer them.

Still, sources close to the investigation point to several interesting facts. For instance, they said, the gun that fired the fatal shot belong to Michaelides.

Further, they said, although the weapon in question was an automatic pistol that ejects spent shells, no such cartridge has ever been found near the site where Sasha Bruce lay.

Sources add that there are also telephone records that show a number of calls made to Tennessee in the days before Sasha's death, and there is speculation by several Bruce acquaintances that Sasha might have learned then that another woman was carrying Michaelides' child.

According to a Bruce family friend, Michaelides himself refused to stay at the hospital as his wife lay dying and insisted instead on returning to the estate.

Papers filed in Charlotte County show that Michaelides resigned his claim to the estate of Sasha Bruce in November 1975, signing it over to her brothers. A month before they were wed, she had redrawn her will, making him sole executor and beneficiary on one condition: That he would have to marry her.

Both Bruce family friends and John C. Lowe, Michaelides' Charlottesville lawyer, agree that the Bruce brothers gave Michaelides at least $100,000 after their sister died, and family friends say it was to buy him out of any claim to Sasha's goods.

Curiously, had Michaelides not renounced his claim to the estate, he might still have received no share in Staunton Hill. A deed on file in Charlotte County says that Sasha had already sold her share to one of her brothers.

The deed is dated Feb. 24, 1975, when Sasha should have been in London. It was not filed with the county until Dec. 29, 1975, nearly two months after she died.

Michaelides, meanwhile, returned to Greece last April 23. He has since been joined by his first wife, and both have refused to discuss any of the above with a reporter.

"No matter how one describes it," one of Sasha Bruce's friends says, "it is a terribly sad story."