The Olympics open next Saturday ablaze in official pageantry and darkened by the bitter truth that in this latest collision between East and West, the Olympic dream is a casualty.

Hundreds of millions around the world will watch as the Olympic runner dashes to the rim of vast, superbly equipped Luzhniki Stadium in central Moscow and brings to life the giant festival torch in fiery symbol of "faster, higher, braver." But hundreds of other millions will shun the dramatic moment as a spectacle made worthless by the invading Soviet arms in Afghanistan.

Bright symbol and dark reality will thread through the entire two weeks of this troubled, boycott-damaged 22nd Olympiad, despite intense efforts by Soviet authorities to contain and cover up their unavoidable embarrassment with angry cries of foul play.

Not more than 82 nations will participate in these Games, making them the smallest in 24 years. The major Western competitors -- the United States, West Germany, Canada and Japan -- are boycotting in protest of the Afghanistan invasion. And many other teams, stung that their presence on Moscow's playing fields implies acceptance of the Soviet military intervention, will not march in national uniforms or carry their countries' flags.

Despite the insistence of IOC Presiident Lord Killanin and the Soviets that politics and sports don't mix, the boycott by the U.S. and other prominent sports nations may rob these Games of significant athletic meaning. Veteran IOC officials think Moscow will be lucky if there are more than 10 world records set in the premier sports of track and field and swimming.

The Soviets are said to have been hoping for far more. Thus, not since the Berlin Games of 1936 have athletics and politicis been intermingled in such confusing and dramatic ways.

Although President Carter's boycott effort fell well short of White House hopes of inflicting mortal damage to Moscow, the cost of the military intervention to the Olympic high command of this authoritarian country has been enormous. Nor more than perhaps half the anticipated 300,000 foreign tourists are expected to attend, cutting hard at the last moment into carefully laid plans to impress the visitors with the stories of Communist Party rule, as well as pumping their hard currency into a troubled economy.

The U.S. pullout triggered a cutback in planned coverage by media world wide, since the centerpiece of gritty superpower competition by Soviets and Americans, which has dominated the Games from Melbourne in 1956 onward, would not occur. Reduced coverage, including NBC's cancellation of its massive television coverage, has further diminished the global impact of the Moscow Olympiad.

For those who do come, the Soviet Union will present a curious pastiche of strong impressions that reflect fundamental realities of Soviet life while at the same time obscuring its subtleties.

The sports facilities lack the profuse sumptuousness of American sports palaces, but will provide excellent utilitarian sites for athletes and spectators. With the exception of final touches, the main Moscow sites of the Luzhniki complex, Dynamo Stadium and the glistening new Prospekt Mira Natatorium and adjoining roofed indooor stadium are ready.

Luzhniki and Dynamo, revered here for more than 20 years, have been completely refurbished, with improved press and spectator facilities and heavy new banks of floodlights for night events.

The indoor stadium, with a capacity of some 40,000, modest by U.S. standards but the largest in Europe, may be the best of the collection. uA huge movable wall divides the stadium in two, say for boxing and gymnastics, and can be rolled back for main floor events. It is well lit, has ample snack bars and other amenities.

Muscovites invariably boast to foreigners about these things if asked point-blank. But quiet listening to Soviets tour groups looking at the sites shows deep skepticism among the people that they will benefit at all from the immense amounts of money spent over hte past five years here and in the other Olympic cities of Kiev, Leningrad, Minsk and Tallinn.

Recently, a woman looking at the Prospekt Mira site snorted with derision when her guide gave the standard line about how all will have access afterward. "I bet," she retorted, "just like the Bolshoi." The average citizen is unable to get tickets to the Bolshoi, which is the domain of party elite, privileged intellectuals and favored foreigners.

Foreigners passing the site likely will delight that a break in the line of stolid apartment blocks discloses a small, glistening Russian Orthodox church standing on a little plot of grass and set off by the dramatic bulk of the indoor stadium behind. They will not know that, two months ago, the empty space was occupied by an apartment building and the church was an abandoned derelict. Other churches, used for such things as a cabbage warehouse, not sparklewith fresh paint and in some cases, expensive new gold-leaf domes.

These are among Moscow's latest secrets, to be kept from foreigners. The authorities in recent months have intensified propaganda warnings about mingling with foreigners. They may be spies and provocateurs, carrying bombs and anti-Soviet literature to undermine the state.

The psychological warfare is an extension of the unremitting repression of dissidents that began three years ago and culminated last January in the exile of Nobel peace laureate Andrei Sakharov to a provincial city, Gorki, closed to foreigners. The authorities were innfuriated when Sakharov publicly supported Carter's boycott and condemned the invasion of Afghanistan.

This "chistka," or purge, has extended to thousands of alcoholics who have been sent out of the city. Unruly or non-conformists workers, and many activists, taking the hint, have cleared town until the end of summer to eliminate the possibility of reprisals.

Anger and disappointment over the boycott, the saturation of the city by more than, reportedly, 200,000 uniformed and plainclothes police, plus unknown thousands of KGB agents who can double as taxi drivers, tour guides, translators and just plain folks, has combined to cast a detectably tense spirit over the city.

In this atmospere, the impulse of French Baron Pierre de Coubertin in 1896 to found the modern Olympic movement as a way of improving international understanding seems more evanescent than ever.

Several days ago, an African athlete sat in a brief pool of sunlight on a broad plaza of the international section of the heavily fenced and guarded Olympic village and searched in a conversation for his reactions.

He was feeling the pressures, he said, of isolation. The village, an efficiently designed and orderly collection of high-rise dwellings and athletic practice facilities, looms across a broad knoll in southwest Moscow, about 12 minutes' but ride from the Luzhniki Stadium where next Saturday Soviet President Leonid Brezhnev is to open the Games with a one sentence speech as required by Olympic rules, then fly back to his vacation on the Black Sea coast.

"I'd like to try to make contact," said the athlete, looking at two tables nearby of young Soviets who were sipping soda pop and smoking. "But they're so guarded. They don't open up . . . I suppose you get used to it . . ." He trailed off and talked about his home country for a while, then suddenly came back to Moscow. "They're sort of like robots . . ."

It was a harsh judgment. He has never seen a cramped Russian kitchen, table heaped with garden vegetables, cheese, cold meats and bottles of cooling carbonated kvass made from black bread crusts, the people toasting and talking the night away about a birth, a divorce, a death, about love and hatred, and, above all else, about fear.

He will see the police and the sports sites, the fans, the competitors. There will be guided tours of the Kremlin and many other of the city's landmarks and he will be impressed by much of this. Most people are. But he is wondering about what goes on behind the faces and eyes of thousands of Soviets moving past him.

Like the rest of the world, it is unlikely he will be able to find out.