THE SCENE in Sheridan that September morning two-and-a-half years ago was bloody and bleak: There, amidst the wreckage of their blown-up automobile, lay the bodies of the exiled Chilean diplomat and one-time ambassador to Washington, Orlando Letelier, and his American colleague Ronni Moffitt, both killed by a conspirator's bomb. The bleakness of that scene, along with the towering sense of outrage it engendered, was soon to be reinforced by the apparent absence of any prospect that the murderers would be found and prosecuted. They were believed to have disappeared into that secure and protected nether world of government agents and double agents and triple agents, where the big wink and the blank stare are all that greet people who are trying to bring criminals to book. Against that background of anxiety and frustration, the conviction of three men in federal court on Wednesday in connection with the murders must be accounted a small but sturdy triumph.

We are not rejoicing in the personal fate of those three anti-Castro Cubans who were found guilty. It is on an impersonal plane that the satisfaction is to be found -- in the amazing beating of the odds against any likelihood that the combined and cumbersome American systems of justice, intelligence and diplomacy could or would pursue the killers across national boundaries and eventually into court. At that, the story is not an especially lovely or inspiring one, or something about which you can be entirely comfortable. The convictions depended in large part on a plea-bargaining deal arranged with one of the conspirators, the American Michael Townley, who confessed to having been an agent of the Chilean secret police (DINA) and to having been acting as its agent in setting the bomb for Mr. Letelier, a voluble and tireless critic of the Pinochet government in Chile. And although the Pinochet government, under American pressure, did cooperate in making Mr. Townley available, it is far from clear that it will further cooperate in making available three Chilean intelligence higher-ups who have also been charged in the killings and who are currently fighting extradition in the Chilean courts.

Nevertheless, especially as we gaze across a landscape stretching far from Sheridan Square, one that seems to be strewn with the gruesome handiwork of terrorists everywhere, we feel rather the way we did when the Hanafi cases were concluded: It counts at least as something that in a particular place at a particular time, a system of orderly, rational justice -- itself the antithesis of terrorism in every respect -- was brought to bear and made to work.