Fleetwood Mac breezed into Joe & Mo's restaurant here on Saturday night, asked to have tables and chairs for 15 arranged in the shape of a guitar (honest) and drank the place dry of Dom Perignon at $55 a bottle.

After paying a bill of some $900, the party moved on to the Polo Club, where Christine McVie danced the waltz with her barefoot boyfriend, Beach Boy Dennis Wilson.

Wilson, who formally announced his intention of marrying McVie next February in a recent People magazine interview, pulled a disappearing act after midnight that had everyone but the D.C. police department's missing-persons unit looking for him.

McVie even had the Sheraton-Carlton Hotel's security detail searching corridors and men's rooms for nearly an hour. He finally turned up, no questons asked and no answers given, and the two of them went off to a piano in the Crystal Ballroom, lit a candle and told curious passers-by that they were composing for a new album.

Susan Goldwater, reached in California yesterday, says that she is there because her mother has been ill.

There is a very "prevalent" but "false" rumor, she says, that she is separating from her third husband, former U.S. ambassador to Switzerland Marvin Warner.

The Warners had Thanksgiving dinner with her parents in Newport Beach, then Warner flew to Florida on business and Susan took her son, Barry Goldwater III, to a hotel in Los Angeles to see friends.

Susan, married previously to Rep. Barry Goldwater (R-Calif.) and Colorado contractor Don Richter, gave up her television career here on Channel 9's "PM Magazine" to marry Warner.

Just when you thought, and maybe even hoped, you'd never need to read another word about Watergate, get ready for some 250 carefully put-together pages that should cause more headlines, including a new theory on the identity of Deep Throat.

Investigative reporter Jim Hougan of Harper's magazine, who doesn't mind working years to fit pieces of puzzles together, started out originally to do one definitive piece that asked questions no one had ever asked before.

By the time he had finished, he had almost a book, which has now been divided into two, and maybe three parts. The first is already in galleys and isn't expected to be in public circulation until Dec. 12 unless there is a break-in at Harper's New York office.

There in Saks Fifth Avenue's fitting room is the shah of Iran's son, Reza, getting outfitted in a preppy new blazer and flannels for school.

Through the curtain from the next cubicle bursts a blithe spirit who gives Reza a bear-hug and a jet-setter's air-kissing peck on the cheek.

The 6-foot-6 ex-NYPD cop who guards Reza has his hand on the shoulder holster under his army fatigues before he realizes that he is merely witnessing a social ritual approximating a handshake and a backslap in other circles.