The view from London's Waterloo Bridge -- up the Thames toward Wren's dome on St. Paul's, down toward the House of Parliament -- encompasses striking symbols of the West's attainments. But the bridge itself is now a symbol of the brazenness of the West's enemies.

Georgi Markov, 49, was walking across the bridge on Sept. 7, 1978, heading home from his work at the studios of the BBC External Services. Suddenly he felt a sting on the back of his thigh and, turning, saw a man bending to retrieve an umbrella. The man, with a foreign accent, murmured "I'm sorry."

Markov did not mention the incident to his wife, but early the next morning he suffered a raging fever and said: "I have a horrible feeling that this may be connected with something which happened yesterday." Markov, Bulgaria's leading man letters before he defected, had received many threats and warnings. One warning said he would be poisoned by a substance, tested in Moscow, that causes a high fever.

Scotland Yard announced that doctors found in his thigh a tiny pellet containing ricin, a rare poison extensively studied in Eastern Europe. There is no known antidote. The pellet was a highly sophisticated bit of murder technology. It was made of a platinum-iridium alloy which the human body does not reject. It was the size of a pinhead and had four openings to hold the poison. A similar pellet had been used in an unsuccessful assassination attempt against another Bulgarian defector in Paris. A few days after Markov died, a lieutenant-general in Bulgaria's security force delivered a speech expressing "the deepest gratitude to our Soviet comrades-in-arms of the KGB for their constant help and comradely assistance."

You can read the book that got Markov killed. "The Truth That Killed" (published by Ticknor & Fields) is the autobiography he broadcast to Bulgaria, thereby enraging the regime. Markov's only child, who was just 2 when he died, asked her mother, "Why did daddy write those things if he loved us?" Her mother replied that daddy thought Bulgaria's rulers would not risk the scandal that might result from killing him.

However, the real scandal is that there is so slight, and so fleeting, a sense of being scandalized by such crimes. The fact is illustrated by, and may have helped bring on, the so-called "crime of the century" -- the Bulgarian plot to kill the pope.

The mills of Italian justice grind slowly, but they grind exceedingly small and are grinding to dust the pretense that the Turkish gunman acted alone. There is now not the slightest reason to doubt that his attack was organized by Bulgarians, who would not have undertaken such an audacious crime without the approval of the highest Soviet authorities.

None of this is news to anyone who has read Claire Sterling's book, "The Time of the Assassins." Her work on this case is the journalistic achievement of the age. Her most appalling evidence strongly suggests complicity by some democracies, including this one, in covering up the Soviet crime. The cover-up that Italian authorities are pulling apart, thread by thread, demands this action:

The U.S. Senate Intelligence Committee should call in U.S. intelligence leaders and march them through Sterling's book, page by page, asking why she singlehandedly learned so much more than the intelligence agencies, collectively, did. The Intelligence Committee should dwell on her accounts of attempts by U.S. agents to discourage her investigations. The real "crime of the century" is the complicity of democracies in suppressing evidence of the Soviet crime, lest relations between East and West become unpleasantly realistic.

What are relations to be with a nation such as the Soviet Union, a nation now kill ing its dissidents by medical neglect? Describing the kidnapping, "in familiar urban- terrorist style," of the Sakharovs, The Economist (of London) says that the extraordinary fact is that this atrocity was not the work of a mere terrorist gang, but an action "approved by Soviet ruling circles," in violation of Soviet law and the equally worthless 1975 Helsinki human-rights undertakings.

It is serendipitous that the six-month anniversary of that kidnapping falls on the eve of the U.S. election. And it is splendid that the machinery of Italian justice has synchronized with the machinery of American electoral politics. This is the 10th consecutive election in which all issues should be secondary to this one: who best understands the task of describing and containing the evil empire of which Bulgaria is a loathsome instrument? That issue is not the main reason why Reagan will win, but it is the main reason he should.