He was a Soviet officer of medium build and well-spoken ways. Last year he helped deal smoothly with some American congressmen visiting Moscow who wanted to talk about greater individual rights and Jewish emigration.

When his untimely death was reported in the Communist Party paper Pravda Jan. 2, rumors quickly spread that Lt. Gen. Victor Semyenovich Paputin, first deputy minister of the Soviet Ministry of Interal Affairs, the MVD of spy thriller notoriety, had somehow been killed in the Soviet invasion of Afghanistan.

This seemed plausible, since Pravda said the senior police offical died unexpectedly Dec. 28, without saying how or where. Paputin, 53, was known to have been in Kabul early that month, conferring with Marxist strongman Hafizullah Amin, who later was slain in the Soviet-backed coup of Dec. 27 that installed Babrak Karmal and touched off an international crisis.

But the mystery of Paputin's death soon deepened. Rumors began circulating in Soviet circles that he had committed suicide at home after being recalled from Kabul to face charges of involvement in a major black market scandal in Podolsk, a provincial city 25 miles south of Moscow.

The rumors, probably inspired by Paputin's MVD collegues, seemed an effort to explain away for Soviets, long used to noting nuances in the official press, why Paputin's death notice had appeared on page 6 of Pravda instead of the front page, as befitted a candidate member of the ruling Central Committee. These rumors also could explain why the obituary of such a prominent official was signed only by Interior Ministry and party officials, instead of by Soviet President Leonid Brezhnev and the 13 other Politburo members as custom dictated.

Then last month new rumors surfaced that Paputin committed suicide after being recalled from Kabul in disgrace because he had botched a crucial part of the Soviet coup scenario -- safeguarded Amin until after Babrak had been made leader. The London Observer said it had been told authoritatively Paputin took his own life as the Aeroflot plane carrying him home from Kabul landed at Moscow's Sheremetyevo Airport. This version is largely supported by reliable sources here. "He never stepped off the plane," one said.

These sources say Paputin shot himself because he realized his failure had shattered Kremlin hopes -- however ill-founded -- of giving the coup a gloss of legitimacy and thereby escaping with relatively little world reaction as they had escaped after their 1968 invasion of Czechoslovakia. He saw the welcoming committee and figured suicide was better than what was waiting for him," one source said.

But Paputin's blunder was only one in a series of miscalculations and surprises that have dogged the Kremlin almost from the start of their efforts to bolster the Kabul Marxists who came to power in an April 1978 coup. Sources here trace the beginning of serious trouble for the Soviets to a series of reported Kremlin meetings last September between Babrak and Nur Mohammed Taraki, then president of Afghanistan.

At these unusual sessions, it is said, Taraki reluctantly agreed to join his Khalq (masses) Afghan Communist Party faction with Babrak's purged Parcham (flag) faction and in turn purge Amin, who had ousted Taraki as effective leader and suppressed the Parcham. Babrak's participation was seen as crucial to broaden that Marxists' base and win back allegiance of disaffected Afghan bureaucrats loyal to Babrak before he had been forced out of the leadership by Amin and into hiding in Eastern Europe.

Taraki returned to Kabul and disaster. Instead of ousting Amin, he himself was killed and Babrak's reappearance ruled out.

The Soviet dilemma was starkly plain: not only was the Moslem rebel movement gaining strength, but it seemed likely that Amin would maneuver for support elsewhere to put some distance between himself and the near-fatal grip of the Soviets. Enter Paputin.

An MVD official for many years and nonvoting Central Committee member since 1971, he arrived in early December in Kabul and must have pursued several roles -- convincing Amin to issue a call for a massive Soviet military intervention already about to begin, and thereby "legalize" it, stilling his fears for his own safety at Moscow's hands, and preparing the way for Babrak's reentry. Paputin failed in all these efforts.

Worst of all, from the Soviet point view, Amin was kill during a Soviet assault on the Durulaman Palace, where he had taken refuge during the sudden airlift of Soviet troops into Bagram Airport north of Kabul. Whether Paputin demanded that Amin issue a formal invitation and was refused, or whether their last encounter boiled into a firefight may never be know. But the takeover plot was in shambles and with it, Paputin's career.

In one of those occurrences that offer news grist for the rumor mills, the Soviets have just named the son-in-law of President Brezhnev as first deputy interior minister succeeding Paputin. Yuri Churbanov, said to be 40 or 41, a stocky man of about six feet with youthful features, is married to Brezhnev's daughter, Galina.

Since 1976, Churbanov has been a member of the party's Central Auditing Commission to investigate party administrative problems and complaints. In recent months, he reportedly has addressed several law-and-order meetings of workers and intellectuals in response to a decree last fall to combat rising crime.

Churbanov's boss, Nikolai Schelekov, 69-year-old interior minister, lives one floor below Brezhnev in the same apartment building on Kutuzovsky Prospekt. A close friend from their adolescent years as metallurgical engineering students in the Ukraine, Schekelov has been sponsored by Brezhnev for major party positions for the past 40 years.

Most sources here think the choice of Churbanov is see kind of "coincidence" that reveals the substance of Brezhnev's continuing relative power within the Soviet leadership.