Tonight's NBC White Paper report, "The Man Who Shot the Pope -- A Study in Terrorism," is less a news broadcast than a trotting-by of scenarios . . . and a trot-by on little cat's feet at that. The chief scenario that NBC News hints might possibly be true is that Mehmet Ali Agca, the Turkish gunman who seriously wounded Pope John Paul II on May 13, 1981, was a hired killer whose employer, whether he knew it or not, was the Kremlin.

This thesis is entirely and sickeningly plausible, but it is never proved conclusively on the broadcast, at 10 on Channel 4. Indeed, diplomatic correspondent Marvin Kalb says in his introduction that "a Soviet connection is strongly suggested but cannot be proved." Then he spends the next hour not proving it.

And yet the report is fascinating in its way, because it brings the vicious realities of world terrorism into a brighter, harsher light. The report doesn't have the raw urgency of, say, Pierre Salinger's ABC News special about the secret negotiations behind the release of the American hostages in Iran (perhaps the more raggedy-looking a network documentary, the more rivetingly and credibly it plays on the air), but at the very least, it's grimly sobering, especially for what it says about the ruthless expediencies of amoral governments.

The assassination of the pope, it is made clear, would have suited the KGB's interest in two ways: It would have silenced the Polish-born pope on the subject of Solidarity and the workers of Poland, and it could have played a role in the U.S.S.R.'s "destabilizing" of Turkey, a U.S. ally. And so -- bang.

Occasionally Kalb and producer Anthony Potter must stretch to make their points. The trial in Rome at which Agca was convicted and sentenced to life imprisonment was only three days long, Kalb notes -- "almost as if somebody wanted to sweep it under the rug." Somebody? Who? The subject is dropped and soon we're getting new lessons in international politics that involve the Turkish mafia and the docile Communist bloc puppetry of Bulgaria.

Kalb and fellow reporter Bill McLaughlin investigate Agca's background. His brother, as surly and unsavory a character as Agca appears to be, says, "It's like the buzzing of a fly to us. We are not afraid of dying." Terrorism runs in the family. Agca was getting terrorist training in 1977 at the age of 19, and McLaughlin stands on the street corner where Agca committed his first murder for profit, the assassination of a Turkish newspaper editor who had angered both the right and the left.

Agca was, McLaughlin says, "a coldblooded killer for hire, a terrorist without ideology." What you wonder is, how many more of them are running around out there right now? This is one hell of a rotten world we're living in.

Not all the summoned witnesses seem particularly relevant. We see interviews with not just one but two hotel clerks who look up Agca's fake name in their ledgers. Footage of Kalb questioning one hotel clerk looks like footage from "60 Minutes"; the producer is saying to us, "Look, Marvin actually went out on his own two feet and interviewed people." It's showmanship, not journalism, and those oh-so-dignified souls at NBC News shouldn't kid themselves.

However, authoritative figures are represented as well, including a former KGB agent who defected. Cardinal Silvio Oddi tells Kalb that "any 007" could harm the pope, because he must remain an essentially accessible figure. Kalb: "Who do you suspect?" Cardinal: "You are going too far." Kalb tries another avenue of inquiry, and the cardinal is willing to say of the assassin, "He was certainly acting in the name of others."

ABC News has taken considerable pains in the past few days to point out that NBC is not breaking new ground with this report and that ABC News raised the possibility of the assassination attempt having been the result of a conspiracy on "ABC World News Tonight" in December and a week later on "ABC News Nightline." But the Kremlin connection, however tenuously it is made by Kalb and Potter, is a new wrinkle.

If the facts and suppositions about terrorism made in this program are extremely disheartening, the incidental portrait of the pope himself that emerges is just the opposite. His efforts on behalf of the Polish people seem all the more heroic when one realizes he had to have been aware of the dangers.

While there is much to commend about this NBC White Paper (except for the fact that nothing on television should be called a "paper"), there is much to deplore about the network's promotion of the broadcast. The show has been ballyhooed as resembling a political "thriller" and on-air ads employ graphics that show the pope as viewed through the sights of a rifle (he was shot with a 9-mm automatic, as it happens). This is the kind of insensitive bad taste that would make even Roone Arledge cringe.