HELSINKI -- Yuri Deryabin, the Russian ambassador in Finland, wears a cardigan sweater and a warm smile as he greets a visitor in his embassy's ornate conference room. Cookies and coffee are offered, along with solicitous small talk. With his slim build and avuncular manner, Deryabin seems in every respect a kinder and gentler breed of Russian diplomat -- soft-spoken, thoughtful, moderate, gracious, even deferential.

So why are so many Finns furious with him? And how come a few zealots have threatened to kill him?

The immediate answer lies in a strange diplomatic incident that led to a firestorm in the Finnish media last month. A confidential note from Deryabin to the Finnish Foreign Ministry was leaked to the press, resulting in blazing front-page headlines the day before first-round presidential voting. Critics thundered that Deryabin was reviving Soviet-style interference in Finnish politics. The outcry went on for weeks.

But the passions surrounding the affair are rooted in the history of two neighbors separated by an 800-mile border, as well as cultural differences and mutual suspicions. And at the core of it all is the strange story of a bit player in the Cold War drama -- the mysterious "Mr. Komissarov."

Now 62, Deryabin first arrived in Helsinki as a diplomat in 1968, already a 15-year veteran of the Soviet foreign service. With his straightforward manner and passable Finnish, English and Swedish, he soon developed a reputation as an intelligent and able pro; he was, in the view of his Finnish counterparts, a "Western-style diplomat."

At the time, Russo-Finnish relations were a curious but durable fixture of the Cold War. Defeated by the Soviet Union in World War II and nervous about the Kremlin's appetite for territory and influence, 5 million Finns could hardly afford the luxury of confronting their 250 million Soviet neighbors.

Under a policy known in the West as "Finlandization," Helsinki kept its mouth shut about Soviet policy and kept its distance from Western security and economic blocs, such as NATO. But while Finland maintained official neutrality, it also set about developing one of the world's most robust and smoothly working capitalist economies.

The downside was that from time to time Finland had to swallow its pride, pay its respects and occasionally kowtow before Moscow.

The low point came in 1961, before another Finnish presidential election. The Soviets noticed a coalition of opposition political parties urging a more Western-leaning policy, and the Soviet Embassy sent a note to the Finns requesting "military consultations." Roughly translated, this meant: Prepare for an invasion.

In a panic, President Urho Kekkonen dashed off to Russia to pay homage to Premier Nikita Khrushchev. The pro-Western parties withdrew from the race. In the end, Soviet tanks stayed on their side of the border, but for Finland the lessons of what came to be known as the "note crisis" were unforgettable.

Deryabin arrived at the Soviet Embassy in 1968 determined to maintain "Finlandization" -- and perhaps improve on it. He was convinced that beyond the awkward handshakes and bland communiques of diplomacy, Finns should know how the Kremlin viewed events in Finland.

He began to write books and scores of articles under the pen name "Yuri Komissarov." A few Finnish diplomats guessed that "Komissarov" might be Deryabin, but in general the author's identity was a mystery. Deryabin now acknowledges a little sheepishly that Komissarov is his wife's maiden name.

The books and articles, forcefully and often eloquently written, were published in the Finnish press. In them, "Komissarov" gave Moscow's line more frankly than any diplomat could. The subtext was: Don't step out of line, don't make friends with the West, don't harbor any illusions that you will ever slip from Moscow's sphere of influence.

To Finns, "Komissarov" was a hard-liner. But Deryabin saw his role as constructive: "Finnish-Soviet relations then had a special feature -- that we never said anything critical of the Finns in public. Our leaders met, signed nice little communiques. But there were problems. . . . I wrote in order to state how Moscow really viewed these positions."

Through the 1970s and early '80s, in 10 years of postings in Helsinki, Deryabin cranked out the "Komissarov" articles. After Mikhail Gorbachev came to power in 1985, Deryabin was recalled to Moscow to work for Soviet Foreign Minister Eduard Shevardnadze, mainly on arms control, human rights and European affairs.

After the collapse of the Soviet Union in 1991, Deryabin returned to Finland in 1992 -- this time as Russia's ambassador. He got a chilly reception. His identity now known, Deryabin's appointment was greeted by many Finns as the return of "Komissarov."

Mindful of his hosts' worries, the ambassador launched a diplomatic offensive. He went to church. He kissed icons. He gave interviews nonstop -- more than 100 in 1993. "From the beginning, I chose the line of openness and told them that 'Komissarov' was gone along with the Soviet Union," he said.

Finns gave him an A for effort, and many forgave him. "When he arrived, he seemed completely transformed," said Olli Kivinen, a leading journalist.

Relations between Moscow and Helsinki were improving. But there were still a few irritants. For Moscow, one was the emergence in Finland of two small groups of extreme nationalists. The groups profess views that are anti-communist, and, to the Russians, fascist.

Last May, Deryabin mentioned the groups to Finnish Foreign Ministry officials. He said Russia was concerned that their activities violated the 1947 Treaty of Paris, which banned the resurgence of fascist groups in Finland.

Deryabin said he mentioned the issue more than once but got no reply from the Finns. One reason may be that Finnish diplomats regard the 47-year-old treaty as all but obsolete, while the Russians do not.

Finally, on Jan. 10 this year, Deryabin wrote a formal note to the Foreign Ministry "asking" if the groups did not violate the treaty. Someone leaked the note to Helsingin Sanomat, the leading Finnish daily. The story ran Jan. 16, one day before presidential voting. To many Finns, it was a replay of 1961 -- the "Note Crisis," Part II.

The media exploded in indignation. At least one presidential candidate said the note had torpedoed his chances and helped a rival.

Many saw a brutish attempt to influence the voting -- although just how was unclear. More serious analysts, including senior Finnish officials, saw the note's timing as a crude effort to reassert Moscow's prerogatives and remind the Finns of who won the war and who lost it.

"I think it was 'Yuri Komissarov' who wrote this note to us," said a senior Finnish diplomat. "It was a private attempt to remind us that we are not quite a free country."

Helsinki's official reply was a barely polite rebuff. Finland would evaluate the case of the two groups in light of Finnish law, not the treaty. The reply noted that Finland is worried about aggressive nationalism in every country, a reference to the rise of Russia's own radical nationalist, Vladimir Zhirinovsky. On Jan. 31, a Finnish nationalist group sent a fax threatening Deryabin's life.

The furor left Deryabin shellshocked. The note was routine and innocent, he insisted; the timing was accidental. If there had been a reply to his earlier, informal query of last spring, he said, he would not have written the note at all.

Few believed him.