It began with a young woman artist looking our her window onto a Capitol Hill street corner late last month. There was a traffic accident and she rushed into the night, trying to be of help. A police officer arrived. In the confusion, she thought she heard him tell her that George Bush, the vice president of the United States, had been shot nearby.

Within days, that wisp of a detail had spun itself into a full-fledged Washington rumor that for the last three weeks has careened around town from city room to locker room, from the Senate Office Buildings on Capitol Hill to the White House itself: Vice President George Bush had been nicked by a bullet in a predawn shooting outside a townhouse somewhere on Capitol Hill.

The tale purportedly included an eyewitness, Secret Service agents and the inevitable piece de resistance -- the cover-up.

The story had everything going for it but the truth.

This rumor was so pervasive and Bush was so exasperated with the false story than on Friday he took the extraordinary step of asking FBI agents to interview him -- even though there is no investigation of the matter.

"We are not conducting an investigation," said FBI spokesman Roger Young. On the matter of the rumor, Young said: "There is nothing factual about it."

Indeed, the story in its various versions, each ripe with explicit detail, is in fact not true. As far as anyone can go in proving a negative, the story has no basis whatsoever.

What was learned by tracing the rumor is the way in which gossip, perhaps Washington's second biggest industry after government, makes its rounds, gains credibility and inevitably causes pain.

This is the story -- almost an anatomy -- of one news organization's double-edged role: that of trying to track down the rumor while at the same time unintentionally but unavoidably helping to spread it. The Accident

The rumor was a child of coincidence, born of one of those encounters between strangers that lie at the heart of city life.

A young woman artist who does not want to be identified by name happened to look out her window last Feb. 1, three weeks before the alleged Bush incident, just in time to witness a murder.

She went outside to offer aid, but the victim, a yound Supreme Court librarian, died in her arms as a D.C. police officer looked on. The artist came to know the officer and another man who had been the murder victim's best friend.

Several weeks later, the same young artist heard the sounds of a traffic accident on the street below. She rushed outside. The first police officer on the scene was her friend from the night of the murder. It was he, the artist says, who told her then that Bush had been shot. "The vice president was shot today," she quotes the policeman as telling her.

Quickly returning to her apartment, the artist tried to find out what had happened. She turned on the radio, expecting to hear it on the news. She heard nothing. She turned on the television. Nothing. She telephoned each of the wire services to ask about the shooting of the vice president. No one knew anything about it. Next she called The Washington Post, then WRC-TV News, Channel 4, where someone on the other end of the phone took her name and telephone number.

The next day the artist mentioned the Bush shooting to a close friend -- the same man, in fact, who had been the murder victim's best friend. No one else. But that was enough; every action she had taken served to spread the tale.

Her friend mentioned it to a legislative aide on Capitol Hill one night as they downed a few beers. The aide told two people -- his roommate, a Justice Department lawyer, and a friend who worked for columnist Jack Anderson.

The story was bursting forth with a life of its own. The Cocktail Parties

A Washington Post columnist was out making the rounds and heard two people talking. One was important -- someone whom she considered an authoritative source. But because she was not part of their conversation, she could only listen. What she heard was this: Vice President George Bush had been shot -- really, only nicked -- as he left someone's house late in the evening. The Secret Service had not reported it; neither had the press.

The columnist passed the tale to a high-ranking Post editor. Several reporters and editors were informed. A call was made to the Secret Service. rNothing -- denials. Calls to the local police -- more denials. Everyone said they'd heard nothing and anyway, they certainly would remember even vague references to such an incident. But they would check. A call to the U.S. Attorney, the chief prosecutor in Washington, yielded similar results -- nothing. Bush's press office was called -- nothing there, either.

Meanwhile, on a different lap of the party circuit, the rumor arrived on the lips of a woman who had heard it from the Justice Department lawyer.

She told another woman.

This time, there were more details, including a Captiol Hill address.That woman told her husband, another Washington Post columnist. He dutifully passed the information along to the same high-ranking editor.

For the editor, that was perhaps the second source. Suddenly, the story moved off the back burner and became worthy of an all-out investigation. First District Police Headquarters

Two weeks on the job, his files yet unpacked, Deputy Chief Ronald D. Cox welcomed two Post reporters to his office in a deteriorating red brick schoolhouse. He threw up his arms, disclaiming any knowledge of unusual events in the Capitol Hill area his officers patrol.

"I have nothing to hide," he said in a down-home twang.

Even as he spoke, a scratch pad lay on his desk bearing the vice president's name, scribblings about a time, a date, a place and the word "assault."

In time, the cryptic scribbling on the precinct house pad would be mentioned to those in Bush's office. Soon, the word in White House circles was that the Post had a "police report" on the case. Not quite. What The Post had was a glance at the notes of a previous conversation the police had had with a television reporter from Channel 4, who had called in his own effort to pin down the rumor. The Inquisitions

When Jack Anderson's reporter heard the story from her friend on the Hill, she immediately set out to find the artist. As the young artist recalls them, the interviews were frightening experiences. The Anderson reporter, she said, gained her confidence by hinting that she wanted to talk about the murder, then hit her with questions about the vice president. Telephone calls and stakeouts followed. Afraid, the artist hid.

The vice president's press assistants also were getting calls. From everywhere: CBS, NBC, Newseek, Time magazine, The New York Times.

Peter Teeley, the vice president's press secretary, told Bush of the inquiries. The vice president was incredulous and was as angry as Teeley had ever seen him. "Jesus, this is the craziest thing I have ever heard," he said. Bush thought the whole thing was silly. "You should call Barbara [Mrs. Bush]," he told Teeley, "and let her know what this is all about." Teeley did.

In the Secret Service offices, the agents assigned to the Bush detail were angry their integrity was being questioned. They were being accused of not reporting a shooting incident involving the vice president.

Their procedures, rules and the code of honor to protect at all costs -- even with their lives -- would require a report. The head of the detail, a very religious man, was particularly upset at the insinuations and questions. There was no indent.

Reporters dug even deeper into the story. One with a good contact in the Secret Service asked the contact to review the records: Was there any incident involving Bush and a shooting? Was some element of the story true?

The answer came back. On March 8, as a motorcade drove west on Canal Road, officers had heard a "popping sound" from a "steep, rocky cliff" on the Virginia side of the Potomac side of the River.

But it had been President Reagan, not Bush. And the noises never proved to be gunfire.

Back to the drawing board. The White House Press Briefing

Tuesday, March 17, 1:51 p.m.:

The White House press corps clamored for the attention of Deputy Presidential Press Secretary Larry Speakes, peppering him with questions about the incident.

Q. "Is the president concerned about the large number of rumors circulating around Washington the last week or ten days that George Bush has been shot at."

A. "You mean literally? . . . You mean fired on?"

Q. "Larry, I think a lot of have heard a rumor and there's more to it. . . . Why don't you see if he was engaged in some kind of situation . . . ?" [laughter]

Q. "And Larry, when did it happen? And did the Secret Service fire the bullet?"

A. "Okay, I will check on the president's concern . . . on the rumor of rumors . . . ." The Witness

Reporters then began to track back through various reports, suspicions and gossip to see where all this might have started. It all led to an artist on Capitol Hill.

Concerned neighbors could not help but notice clusters of reporters camped out by her doorstep. It seemed that as one stakeout left, another appeared. Many of the neighbors had heard the story from reporters pounding on there doors. "Will it hurt my property value?" queried one worried resident.

At first the witness declined to answer any reporter's questions, but most of them returned, interpreting her silence as knowledge. She felt harrassed. One of the television stations had sent reporters with cameras in tow. And the persistent Jack Anderson reporter had left only after the artist threatened to call the police.

However, finally persuaded that it made sense to unravel the tale, she agreed to a secret meeting.

The artist was very precise. She knew only one thing:

The night of an automobile accident on her street, Feb. 22, she had heard a officer say, "The vice president was shot today." She knew and trusted the officer because he was the same one she had met weeks before at the scene of the murder.

I thought that's what I heard him say and I didn't have any reason not to believe him," she said.

The officer disagrees, emphatically: "I donht know anything about it. I didn't say it and I didn't hear it . . . . I don't know what you're talking about."