Arkady Nikolaevich Shevchenko opened last night with a joke.

"Fresh joke from Moscow about Gorbachev," the bestselling celebrity defector told his audience. "It's about how he has been elected, or selected, for general secretary. Initially most of Politburo opposed him. But then they asked the doctors and the doctors said he had 18 months to live." Everyone was all ears. "And after that he was unanimously elected!"

The Kalorama penthouse rippled with laughter. First Shevchenko's -- a loud, buttery laugh. Then, together in a chortling mass, the low chuckle of CIA Director William Casey, the restrained giggle of Supreme Court Justice Sandra Day O'Connor and the laughs of 25 others -- even the hearty guffaw of Ernest Hueter, a one-time professional gag writer, now a think-tank head, who lent his apartment for the occasion.

It was a soiree set up by Ernest Lefever and his conservative brain trust, the Ethics and Public Policy Center, to bring together like minds for food, fun and facts. Most of the guests -- a few reporters, a congressman or two and assorted Washington types -- came to hear the former Soviet diplomat, erstwhile American spy and current famous writer (author of "Breaking With Moscow") on Mikhail Gorbachev. O'Connor said she was there as a friend and neighbor of the Hueters. And Casey was there for the intelligence of it all.

"What brought me here is I've never met him before," said the CIA director. "He might have some insights." He said he hadn't bothered to peruse Shevchenko's file. "Why should I? He's a free citizen."

Indeed, Shevchenko, a busy lecturer who, according to his booking agent, receives fees as high as $20,000, was doing this one for free.

"When you're a millionaire," said his agent, Joe Cosby, "you can afford to be a little generous."

After drinks and dinner, Shevchenko spent an hour and a half warning his listeners that despite Gorbachev's dynamic image, "the Soviets still lie. The Soviets still cheat." He said that in the upcoming Geneva summit, the United States should not make concessions.

"If you make concessions, the Soviets think you are naive, stupid idiots."

To which William Casey mumbled wryly, "We are." And society columnist Betty Beale, sitting beside him, proclaimed brightly, "We are!"

Casey, sandwiched between Beale and Shevchenko's American wife, the former Elaine Bissell Jackson, on a sofa, sank farther and farther into the cushions as the evening wore on. While Shevchenko assessed the Soviet leader's strengths and weaknesses ("There is millions of people more brilliant than Gorbachev in Soviet Union -- even his Russian is not so perfect"), the intelligence director closed his eyes.

During an extended discussion of structural problems in the Soviet economy, he slouched back, eyes firmly shut, his chin resting on his tie. Finally the talk moved on to the Soviet adventure in Afghanistan, and Casey resurrected himself, lifting his lids. But at length the sinking, shutting process began once again.

Shevchenko, pacing the room with water glass in hand, seemed not to notice, taking one question after another, and answering in full.

"In 25 words or less, Arkady," Elaine Shevchenko instructed when someone asked about American-Soviet computer technology transfers.

She was admirably terse when questions were put to her.Asked about a novel she is hard at work on, she said, "It's a silly romance." Pressed, she said things like "Fine," "I don't know," and "I need a cigarette."

"What can I say?" said Justice O'Connor when it was all over.

"Good, excellent, right on the nose," was Casey's appraisal.

"Wonderful," said one of Casey's security detail, who spent the night standing outside in the hall.

The hosts, too, seemed pleased. Ernest Hueter, who became a bakery executive after giving up gags, runs the National Legal Center for the Public Interest. His wife Joan is with the National Association of Pro America, which she described as a group "founded in 1933 by Mrs. Theodore Roosevelt."