Diplomacy is back on track.

Smiling their party smiles and dressed in their black-tie best last night at the Kennedy Center, the key players from the Wednesday night slapping drama -- Sondra Gotlieb, wife of Canadian Ambassador Allan Gotlieb, and Connie Connor, her social secretary -- faced Social Washington with their upper lips stiffly in place.

And Social Washington, eager to have its dictums of decorum put back in order, embraced them.

It was a simple question: How do you feel tonight?

Gotlieb's answer: "Well . . ." She looked into the air above guests' heads and seemed to think seriously about how she felt.

"She looks terrific!" blurted Nancy Dickerson, coming quickly to the aid of her "good friend." Dickerson had walked into the champagne reception with Gotlieb, fur coats leaning into each other.

"I deeply regret this happened," said Gotlieb of the incident, in which she slapped Connor at an embassy dinner for Canadian Prime Minister Brian Mulroney.

"I know Connie's here tonight," said Gotlieb, who looked somewhat shaken and received numerous hugs from friends at the party, although she didn't spend much time with Connor.

"All I can say," said Gotlieb, "is, to err is human. I apologize. I feel terrible about it and I really can't say any more."

Connie Connor didn't say much more either.

"I hope it blows over," she said, calling the whole episode "dreadful, dreadful."

Things are all patched up?

"They were five minutes afterward," said Connor.

The reception, concert and dinner were planned at least four months ago to celebrate the visit of the Montreal Symphony Orchestra in the Concert Hall. The champagne reception was held by Grant L. Reuber, president of the Bank of Montreal.

And the ambassador and his wife were the guests of honor.

When the Gotliebs walked into the reception, photographers immediately started snapping pictures and calling out at them to pose with various guests. Federal Reserve Chairman Paul Volcker was pushed into one group next to Sondra Gotlieb.

"Oh, no, I'm too controversial," he joked.

Other guests smiled and gripped their glasses a little bit tighter when they talked about the slap. And everyone seemed to be going out of his way to be supportive.

"I have no comment at all," said bank president Reuber. "The Gotliebs have very distinguished reputations in this city and I have great admiration for them . . . She is a friend of mine."

Said Dickerson, with a broad smile: "I love her." She then turned the floor over to Deputy Secretary of State John C. Whitehead.

"Doesn't seem like such a big deal to me," said Whitehead.

"I think she's got style and verve," said Roy Pfautch, president of Civic Service Inc., who met the Gotliebs through his friendship with former Canadian prime minister Pierre Trudeau.

"I think there is a tremendous degree of pressure to constantly be on stage," Pfautch said. "Those of us who let go occasionally handle it differently than others. I have seen her be as warm and gracious to someone who's new as she is to one of the older 'in' names."

And Pfautch said he thought Social Washington was a forgiving bunch.

"I think there's more of a heart in this town than most outsiders give us credit for. People go the extra mile."

As the reception was breaking up, a photographer requested a shot of Connor with the ambassador.

"You want a picture?" she asked. "Sure, he's my buddy." As the two of them faced the camera, Connor smilingly offered Gotlieb a little advice. "If you say 'washing machine,' it comes out better," she said.

"Washing machine," he repeated.

Yesterday, ambassadors' wives and social secretaries were hit hard by the news of the incident. In their voices you could hear, "There but for the grace of God go I."

"Bad news today," sighed Countess Ulla Wachtmeister, wife of the Swedish ambassador. "People don't understand that this is a job like any other . . . Anyone can be very tired . . . I'm sure she was just overtired and didn't mean it. There was too much going on at the same time."

"It's hard to be so high-profile," said Cecilia McGhee, wife of former ambassador to West Germany and Turkey George McGhee. "I feel for her."

They're supposed to be quiet emissaries, these diplomats' wives, cultivating overseas relationships, attracting only favorable attention and giving countless dinners that they can only hope will turn out blissfully. So when one steps out, beyond the staid realm of protocol, tongues wag and flashbulbs pop.

Who can forget Margaret Jay, then the wife of former British ambassador Peter Jay, showing up at public events with Carl Bernstein? Or Helga Orfila's eye-popping de'colletage at the otherwise correct White House party celebrating the signing of the Panama Canal Treaty?

At the Canadian Embassy, spokesman Bruce Phillips said Sondra Gotlieb was simply not taking calls. Neither was Connie Connor, who was back at work.

Mulroney's press secretary, Michel Gratton, reached in Ottawa yesterday, said the slapping incident would not have any effect on Allan Gotlieb's role as ambassador.

"The ambassador has done an outstanding job," he said.

To a question about whether Gotlieb could be recalled, Gratton said: "Nobody is appointed for life; at some point in an ambassador's career, he is called upon to do something else. But it would be a mistake now to link this with something that happened that was a very personal matter. The prime minister is very satisfied with the work of the ambassador. The last two meetings with President Reagan went very well, and the relationship is going very well."

"The incident is closed as far as she is concerned," said Phillips, "and the same is true of Connie."

*But it was far from closed along Embassy Row.

"When you're in the Foreign Service, it's not uncommon that the roof falls in and the whole thing blows up," said the wife of a retired Foreign Service officer who asked that she not be named. "The stresses and strains of the life style are such that the sympathies are with the slapper."

"At all times you have to be diplomatic," admonished former chief of protocol Leonore Annenberg. "I think at all times one must behave in a circumspect manner." But then, slipping into her protective mode and perhaps remembering her role as the wife of former ambassador to Great Britain Walter Annenberg, she said: "Sondra is a friend of mine and I wasn't there. I can't comment on the incident."

"I'm very sorry for her," said a European ambassador's wife who did not want to be identified. "We all have our prime ministers or our presidents coming. It happens all the time. That's just the way Washington is. But if the food is not perfect or some other detail, I really think the relationship between people is more important.

"No matter what went wrong, I would never slap anybody. That's not in my makeup."

"No, no, I am a very calm person," said Wachtmeister, asked if she had ever hit anyone herself over a dinner. "I have less of a temperament . . ."

"I don't slap people," said Anne Merete Petrignani, wife of the Italian ambassador. "Not even my husband."

Of course, there's another side to this story, and it seems only fair to give Washington's overworked social secretaries the last word.

"Heavens no, I have never been hit," said Helen Smith, social secretary to the Chilean ambassador. "I should say not. I have worked for wonderful people -- Pat Nixon, the Saudi Embassy -- I have never worked for anyone who would ever do a thing like that."

"Do you honestly think that I would tell you if I'd been hit?" said Mitchell McGlouthlin, social secretary to the Spanish Embassy. "I didn't believe it when I read it."

Said a social secretary who asked to be unnamed: "Everybody has a breaking point, more for some people than others. Sometimes I've thought, 'God, if only I could throw something.' I usually stomp my foot. But I do feel so sad for both of them. You put so much work into something."