The first problem is to explain what exactly Charles Busch, who opened a one-man show at the Vault Theatre last night, does. He is extraordinary and quite brilliant, but how do you explain an actor who performs an entire party of people?

Busch, a slim young man with a mane of brown hair that allows him to appear androgynous, creates not only a cast of characters but a plot as well, with only himself, a simple costume, a chair and lighting. His first piece, "A Theatrical Party," takes place at a party given by one Anton Troy (one of the few characters he does not introduce us to), an English matinee idol who is looking for an actress to play in his upcoming season of "Cleopatra," "Hamlet" and "Romeo and Juliet."

Along the way we meet Rodney Barrington, a young actor; Vivian Perneau, the most vicious theater critic in London and Barrington's suitor; Dame Beatrice Fortesque, an aging queen of the stage; Solange Gabrielle, a minx of a French star; Sir Basil Basewater, a writer of mystery stories, and his "paramour," Lady Lettitia; not to mention the Cockney maid, her boyfriend, a budding American starlet, Troy's illegitimate son and Dame Beatrice's dog.

Busch mixes mimicry and pantomime, pathos and satire, and somehow comes up with a captivating play. He is more than an impressionist because (with the exception of a Katharine Hepburn imitation by the young American actress) he does not recreate specific, famous people. Rather he feeds off cliches, using them as the raw material that he then embellishes with the more complicated techniques of acting. He's sort of like the life of the party carried to the ninth power. He does voices, as good storytellers often do, but then carries it that much further to create in a few seconds a whole person.

He has total control of every muscle, it seems, rearranging his lips, eyebrows, shoulders and cheeks at will. A beautiful young girl turns into a jowly old man; a middle-aged coquette becomes a Cockney workman. There is a touch of camp to all this, to be sure, but it is not female impressionism or limited to jokes about old movies.

In the second half of his show, "Out-takes from 'B' Movies," Busch does a horror movie in a little more than 15 minutes, complete with a "possessed" child who talks to a set of "voices" that include an Irish nun, a Chinese laundryman, a southern belle and a street dude. He winds up with "That's Show Biz," clips from the movies of Lola LaMare, a former movie queen. This last piece is basically a riff of different voices spun out with baffling speed, tapping nearly every 'B' movie cliche from the Queen of the Amazon to a nightclub singer in Chicago. It's a display of virtuosity that seems designed more for a nightclub audience; it's amusing, but without the plot interest of the other two pieces.

Charles Busch will be at the Vault, 1789 Columbia Rd. NW, as part of the Washington Theater Festival through July 19.