Something unique happened in Washington last week: officials of the government joined the relatives of a defector-spy to reveal a mass of detail about a fantastic -- but genuine -- spy story.

The facts already disclosed and new information hitherto unreported raise more questions than the answer but that may simply be the difference between the neat world of spy fiction and the messy reality of actual espionage.

The case involves a man named Nikolai F. Artamonov, or Nicholas G. Shadrin, depending on when and where you knew him. His story would satisfy the appetites of any addict of say fiction -- except for one crucial shortcoming.

The spy novelists rarely leave their readers dangling: each spy tale is complete unto itself. The case of Artamonov/Shadrin, however, is anything but complete. It has no ending only loose ends.

The introductory chapters are easy. In 1959, Artamonov, a tall handsome and unusually young Soviet naval captain, sped across the Baltic Sea from Poland to Sweden on a small launch, carrying with him a Polish woman who became his wife.

He asked to defect and was interrogated by the Central Intelligence Agency. Some of those who met him then were suspicious of his motives for defection, but later, in Washington, his "bona fides" were accepted. Artamonov became Shadrin, and went to work at the Defense Intelligence Agency.

In 1966 the FBI "turned" Artamonov/Shadrin into a double agent. He had a series of encounters with Soviet KGB agents here, in Montreal and in Vienna. During the last such encounter, to Dec. 20, 1975 in Vienna. Artamonov/Shadrin disappeared.

Now a few of the mysteries:

By Artamonov/Shadrin's own account, he was approached in Washington by KGB agents in 1966. They asked him to spy for his original homeland, he later told the FBI, to whom he immediately reported the encounter.

The FBI, asked him to play along --to become a "double" agent. After some cajoling, he agreed, and told the KGB agents he would cooperate.

But how had the KGB found him in Washington? Perhaps it wasn't so difficult -- he did not have a "deep" cover. More curious is Artamonov/ Shadrin's original reaction to that first KGB approach. How would a defector react to such an approach? Wouldn't he tell the Soviet agents to jump in a lake? Wouldn't he be terrified of them?

Somehow, Artamonov had the instinct or inclination not to send those KGB men packing. He left open the possibility that he might work for them, and then went to the FBI.Why?

[Senior officials who have followed the case have no answer to this question, or to many others. The written record is massive, but also inadequate. That recruitment is one of many holes in the story.]

In 1972, Artamonov/Shadrin went to Vienna to meet his KGBcontacts. The FBI approved the trip. The Soviet agents took him to a secret hideout in Austria for several days, giving him training in the use of various espionage devices. He left them with a fancy new radio and other equipment, and returned to Washington.

By that time Artamonov had been "helping" the KGB for six years.He had received new training, instructions and equipment -- Well placed, one might think, to begin some serious spying.

But as far as the FBI ever knew, the KGB ignored Artamonov/Shadrin for nearly three years after he returned from that trip to Vienna. Artamonov/ Shadrin reported no KGB contacts, whatsoever until late in 1975, when the Russians asked for a meeting.

That long hiatus is baffling. But not so baffling as Artamonov/Shadrin's next move. Yes, he told the KGB, I can meet with you -- how about Vienna again? Apparently, he proposed the Austrian capital.

Perhaps this was simply an inspired gambit by a clever double agent, meant to convey both trust and self-confidence to the KGB.

But was that necessary? Artamonov /Shadrin is described by his wife and her lawyer as a man who was originally reluctant to act as a double agent. Nine years later, he is depicted as a man who voluntarily enhanced the enormous risks he was taking by proposing a rendezvous with Soviet intelligence in a remote capital close to the Iron Curtain and far from the American agencies that could best protect him. Why?

These are mysteries that suggest something wrong with the official --and family -- line that Artamonov/ Shadrin was a loyal American citizen (as a result of an act of Congress) only doing his patriotic duty. But if one postulates that in fact he wasn't a double agent but a triple -- a Soviet plant from the outset -- then other aspects of the tale challenge that theory.

Artamonov/Shadrin picked a funny time to go back to the Soviet Union, if that is the interpretation one would like to put on his disappearance. He had a meeting on Dec. 18 in Vienna with two KGB agents, then agreed to see them again on theanyway? Why did he bother with the second meeting if his intention was to return to the Soviet Union anyway?

Why did he leave medicine that he needed to take on a regular basis in his Vienna hotel room? And his reading classes? Why had he just ordered a fancy new car in Washington for delivery soon after he was scheduled to return from Austria?

If he was a triple agent, a Soviet plant, then Artamonov/Shadrin is one of the great overachievers of the cold war -- a genuine espionage hero, who pulled off an unprecedented coup. If that is the case, why haven't the Russians produced him in public, put him on television, awarded him the Order of Lenin? A coup of this sort would be a devastating victory in the war of nerves between the CIA and the KGB, but it would only be a victory if it were palapable, undisputable. Most senior CIA officials now believe that Artamonov/Shadrin was an innocent victim, not a triple agent, so if the KGB deserves credit for a coup, it isn't getting that credit.

The Soviets certainly aren't claiming any coups. In a message to then-President Ford. Leonid I. Brezhnev said last December that Artamonov/ Shadrin had repeatedly asked to be allowed to return home, beginning in 1966. But, Brezhnev said, he disappeared from Soviet view, too.

Yuli Vorontsov, the smooth and clever minister in the Soviet embassy in Washington until earlier this year, raised the Artamonov/Shadrin case with a Ford Administration official several months after his disappearance. "What have you done with him,? Vorontsov asked the American. "His wife in the Soviet Union is worried about him, she wants information." (Artamonov/Shadrin did leave a wife behind when he defected.)

What was the point of this gambit? Wasn't Vorontsov being too cute?

And where is the man today? There are only theories. Many ranking American officials fear he is dead --executed deliberately by the Soviets as a traitor, or by accident in some sort of KGB caper. Some officials wonder if he disappeared voluntarily, in despair at the difficulty of his weird life, suspended between two nations and their intelligence agencies.

His wife insists that he is alive in the Soviet Union, though the evidence of this is circumstantial and dubious. It is difficult to see how any Soviet official can now acknowledge that Artamonov/Shadrin is living in the Soviet Union, given Brezhnev's personal assurance that this is not the case.

And what should an ordinary citizen make of this episode? In the end there is little to go on. Much depends on Artamonov/Shadrin himself. What sort of man was he?

Handsome, big, outgoing, charming --much. He knew many people from his intelligence work, from his private life, from his academic pursuits. (He completed a Ph.D. at George Washington University in 1972. His dissertation was called "Development of Soviet Maritime Power.")

According to government officials, his colleagues and friends repeatedly testify to his loyalty to America, his honesty, his reliability. Those who have cast doubts on Shadrin to this reporter are generally professional skeptics, including people whose job it is to be suspicious about Soviet defectors.

But suspicion remains: the President's Foreign Intelligence Advisory Board, for example, investigated the case and said it could not thoroughly dispel suspicions about Artamonov/ Shadrin's true status.

Perhaps the doubters have an unfair advantage. No matter how persuasive the testimonials of friends and colleagues, no matter how strong the circumstantial evidence, a skeptic can always reply. "Yes, but if he was a brilliant triple agent, then of course he could fool anybody." Just so.

If the American intelligence agencies had handeled the case more professionally, there might be many fewer mysteries to resolve. For example, the FBI turned Artamonov/Shadrin into a double agent without consulting the CIA. Rivalries within the American intelligence community are obviously fierce, and the energy spent on them may sometimes exceed the energy devoted to real work.

When Artamonov/Shadrin went to Vienna for his last meetings with the KGB, the FBI would not allow the CIA station in Vienna to provide surveillance of his movements. The FBI apparently did not know that the U.S. consulate in Vienna was ideally located in view of the church steps that the KGB designated as their meeting place with Artamonov/Shadrin. Surveillance would have been easy.

If Artamonov/Shadrin is an innocent victim of the spy game, then so too is his wife, Blanka, a dentist who practices in suburban Virginia.

By her account she never knew her husband was a double agent. He told her, she says, that he was working secretly with some Soviets who wanted to help the United States. Only after he disappeared and she was on a plane back to America did a U.S. official inform her that her husband had been a spy. She went home to McLean, Va., but heard nothing from the government. Finally she hired a lawyer, and began demanding that the government do more for her husband. She is still making these demands.

But the Polish-born Mrs. Shadrin is not immune from the suspicions that surround this case. Some of the professional doubters in the intelligence community even question her bona fides. Why did she telephone Poland from Vienna in December, 1975.

"I always call home when I am in Europe," she replied indignantly Friday. When asked. She seems furious at the suggestion that there is anything fishy about her or her missing husband.

But spying is a fishy business, and this is a spy story, no matter how it ends.