IT IS EASY to see why John Reed so fascinated Warren Beatty that he made a 3 1/2-hour movie about the man.

Until "Reds" came along, most Americans vaguely knew Reed as the half-mythical author of "Ten Days That Shook the World" who died young and was buried by the Kremlin wall. But the film has given that short life branches and roots, so that it seems to reach into other lives, to make connections all over the world, back into the past and forward to our own time, conjuring names as remote and various as Tchaikovsky and former Maryland Sen. Daniel Brewster.

There are people whose gently reared mothers danced with the future revolutionary when he was at prep school in Morristown, N.J. For Jack Reed was, as the historian said, "as American as apple pie and store cheese." The basic facts of Reed's 33 years (minus three days) are told with fair accuracy by the film, though it does go slightly overboard on the struggles of Reed's wife, Louise Bryant, to reach him in Moscow before his death.

The loose ends are what intrigue you.

What happened to Louise Bryant?

He had married her in 1917 after living with her off and on during the exuberant Greenwich Village interlude. She had run away from her Portland, Ore., dentist husband to share Reed's skyrocketing fate, had witnessed the Russian revolution with him and written a book about it. She fainted at his funeral after he died in Moscow of typhus in 1920.

A New York Times correspondent wrote: ". . . There were speeches in English, French and Russian. A mixture of rain and snow was falling. Although the poor widow fainted, her friends did not take her away. It was extremely painful to see this white-faced unconscious woman lying back on the supporting arm of an official who was more interested in speeches than in human agony. . . ."

Three years later in Paris, Louise married William C. Bullitt, whom she had known slightly in Washington. The wealthy Philadelphian, then the State Department's Russian revolution specialist, had been a friend of Reed's but had proved less than helpful when Reed needed him. In any case, the courtship was the sensation of Paris, climaxing when Bullitt discarded his fashionable Philadelphia wife Ernesta Drinker and married Louise. They had a daughter, Anne Moen Bullitt, born in 1924.

But Bullitt was a cold man, as Barbara Gelb writes in her book "So Short a Time," and Louise started drinking in her unhappiness. (The biography has just been re-issued in paperback by Berkley Books.)

There is a Reed family story that when Louise's former mother-in-law visited her in Paris, Louise confided wistfully, "If Jack were somehow to walk into this room right now . . . I'd leave with him."

Bullitt divorced her in 1930, taking the daughter to his estate in Ireland. Louise returned to the Village as if trying desperately to recapture something of the old life. Aged by alcohol and drugs, she began disintegrating sadly. Friends hardly recognized her blurred features. In 1935, now a bleary 48, she returned to Paris.

"She was in the lowest stage of degradation," writes Janet Flanner, the longtime New Yorker Paris correspondent. "One of the last times I saw her was on a rainy night when I was walking along Rue Vavin in Montparnasse. Literally out of the gutter rose a terrifying creature. Her face was so warped I didn't recognize her."

Louise died Jan. 6, 1936. It seemed to be what she wanted.

Her daughter grew up in Ireland and in the Washington area (Foxcroft School). Her father was Roosevelt's first ambassador to the Soviet Union, the first diplomat granted an audience with Stalin (who by the way can be glimpsed in a crowd scene in "Reds" but appears nowhere in the book). He died in 1967, having traveled far ideologically.

In April 1967 Anne Bullitt married Maryland Sen. Daniel B. Brewster, her fourth husband. They had been engaged in about 1942 when Brewster was serving in the Pacific with the marines but had called it off. With her third husband, Nicholas Duke Biddle, she had lived in County Kildare, Ireland, and it was to Ireland that Brewster retreated when his senatorial career ended. They were divorced a decade ago, and today, using her maiden name, she breeds and trains horses there, professionally. She has not remarried. The Nephew

THERE IS a John Reed who lives in Chevy Chase: a nephew, named after his "Uncle Jack." Reed, a retired Foreign Service officer born three years after the famous radical died, is the son of Henry Reed, John's younger brother, who died in 1954.

The younger John Reed turned over most of his uncle's papers to Harvard's Houghton Library. He did keep a delicately illuminated manuscript of poems written by Jack for his mother in 1910, the year Jack was graduated from Harvard (along with T.S. Eliot, Hamilton Fish Jr. and Walter Lippmann). The youthfully dashing poems are fancifully signed "Jon Rid," the name, so like his own, of the hero of "Lorna Doone," a romantic novel that Jack Reed adored.

"Although my grandmother and father did not share his political views, they were devoted to him and always spoke warmly of him," the nephew -- who himself had difficulty getting clearance with the 1950s McCarthy-era State Department, solely because of his uncle -- has written in a memorandum. "Other contemporaries of Uncle Jack whom I met while I was at college or at other times described him as exuberant and outgoing. Controversial? Certainly. Outspoken to the point of bluntness? That he could be. But also I built up an image of a generous, strong-willed free spirit, full of enthusiasm and seeking to experience life in all its forms."

Most of the family, which includes John, a former journalist with the San Francisco Chronicle and Congressional Quarterly, and his brothers Francis and Henry with five daughters among them, have seen "Reds" and liked it.

"Uncle Jack has been described as a dilettante, a dabbler in radical causes, a playboy. Yet he was unafraid of public censure, physical discomfort and jail . . . He believed deeply in the right of dissent; it was one of the major elements in his character. The other, I think, was his belief that through labor and political action the working man, the 'ordinary' man, could move from relative powerlessness to greater participation in his own life and shape his own destiny."

Like many others, Reed feels that Jack would soon have rejected the Bolshevik revolution and may even have been in the process of losing faith in it when he died. "I'm sure that had he lived, he would have been disillusioned with Russia. He was such an idealist."

The Soviet regime apparently felt the same way about him. Lenin himself wrote the foreword to "Ten Days That Shook the World," but within a decade Stalin banned the book throughout the Soviet empire. Then, after Stalin's death, it came back again, newly translated into Russian. It now had, however, an unsigned postscript to the foreword undercutting Trotsky, who is very big in the book, as he is in history -- outside Russia. The Other Faction

WHEN "Reds" was first screened in Washington, a woman in the audience suddenly yelped and almost jumped out of her seat. Her father was in the picture.

"There he was: Lewis Fraina!" said Olga Corey, a veteran Washington hand who used to run the Illinois state office on the Hill. Fraina, later to change his name to Corey, headed the Communist Party of America, the splinter formed along with Reed's rival Communist Labor Party when the Socialist Party purged its left-wing radicals in 1919. Fraina, portrayed in the film by Paul Sorvino as heavyset, actually was "skinny with glasses and curly hair and a deep, deep voice, the only man who could speak in Cooper Union without a mike," his daughter recalled. "I loved the movie. I cried a lot."

Fraina went to Russia the same time as Reed, seeking endorsement of his group. Later the two men were reconciled, and soon after Reed's death Fraina broke with the party to join the Socialists. A brilliant mind with an eighth-grade education, he became a proofreader in New York, wrote his bestselling "Decline of American Capitalism" on a Brookings Institution grant, later was a strong union leader and an economics professor at Antioch College.

Then, in 1951, the heyday of the infamous Joe McCarthy, the Italian-born Corey fell afoul of the FBI and was threatened with deportation under the McCarran Act. He arranged to sail to Cuba and re-enter on a visa. On Christmas Eve, 1952, the deportation order arrived. The union leadership turned on him. He suffered a heart attack and cerebral hemorrhage and died. The Cuban visa arrived the next day. The Comrades

AND EMMA Goldman, the celebrated anarchist, that disciple of Kropotkin who in 1919 actually was deported? Who called out gaily as the transport left the New York pier, "We expect to be called back to Soviet America!"

After only six months of life in Russia, she wrote to a niece in America that the regime of Lenin and Trotsky was just another form of despotism. In 1921 she and her comrade Alexander Berkman (he who had tried to assassinate Henry Frick during the Homestead steel strike) turned against the Bolsheviks and fled to Finland. Eventually she settled in Canada, lecturing and writing such books as "My Disillusionment in Russia" and "My Further Disillusionment in Russia." She died in Toronto in 1940, aged 70.

Another comrade, William (Big Bill) Haywood, of the International Workers of the World, who had jumped bail and fled to Russia in 1921, died there seven years later at 59. He, too, is buried at the foot of the Kremlin wall.

Max Eastman, the editor and poet, Village radical and faithful supporter of John Reed, lived the longest of them all, dying at 86 in 1969.

The "witnesses" in "Reds," people who knew Jack Reed and his times, bring to the picture a brisk gust of reality even as their lined faces connect us with the past. One of them, the radical author Scott Nearing (of whom Trotsky said, "We will deposit . . . Scott Nearing on the scrap heap of revolution!") is 98 and going strong. Another is Galina von Meck, who had seen the revolution firsthand, like Reed.

She happens to be the granddaughter of Nadezhda von Meck, the famous "beloved friend" of Tchaikovsky . . . a human link, a messenger of time, an envoy from an orderly, impossibly distant, vanished world, from a Russia not yet even dreaming of Lenin and chaos.