TRICKS OF THE TRADE by Sidney Michaels; directed by Gilbert Cates; sets and lighting by Peter Dohanos; costumes by Albert Wolsky; incidental music by Charles Fox; produced by Gilbert Cates and Matthew Alexander.

With George C. Scott, Trish Van Devere, Lee Richardson and Geoffrey Pierson.

At the National Theater through Oct. 26.

Did you ever, when you were small, receive a birthday present that came in a marvelous, huge, rainbow-colored package that promised something exotic and wonderful like a parrot or a Go-Kart? And did it ever turn out to be a shirt?

That's how it was with the box they tore open at the National Theatre tonight. All those fabulous ribbons and tassels! All those tantalizing shapes-within-shapes! All that hoop-de-doo as they ripped away layer after layer of mysteriously scented wrapping paper . . . and then, gradually, the hideous, creeping sensation that in the innermost reaches of this great fried wonton of a dramatic entertainment, there was nothing remotely worth waiting for.

It's enough to make a person primally scream.

Or, as Dr. Augustus Browning himself remarks during a pause in the unveiling, "Sometimes an axe is as good as a can opener."

Dr. Browning is the hero of "Tricks of the Trade," a comedy/suspense trifle that has paused in Washington on its way to Broadway. He is also George C. Scott, and that's a crime -- to wit, deceptive advertising. What a joy it is to watch this crafty old actor heave himself about the stage, paunch foremost, chain-smoking any cylindrical thing he can stick his lips on, guzzling booze from the bottle, and generally acting like the utter, lovable antithesis of the expensive New York psychologist he is said to be.

"I want you to understand something," a patient tells him. "I'm not crazy."

"Of course you are!" Scott fires back, with a voice so gravelly he sounds like an old 78 record being played through a broken needle.

Today's patients, he bitterly complains, just won't lie down anymore. The couch is too tired a cliche. And such an expensive couch! Genuine leather, but what can he do? "A shrink without a couch is like a pawnbroker without the three balls."

The repartee comes on a little aggressively now and then, but Scott makes it all very jolly and seductive. And with the experienced assistance of playwright Sidney Michaels, he gives the audience every reason to anticipate being plunged into murky deeps as entertaining and satisfying as the bright surfaces where we began.

To begin with, only one thing is clear -- that nothing is clear. Augustus Browning is no mere overpriced headshrinker. We know that. He has these acquaintances, after all, who work for an agency called "The Agency." And there are hints dropped about a friend named Harry -- "sort of a business partner," Dr. Browning explains -- who was murdered in Czechoslavakia, but managed, as he died, to pass a certain secret something to the doctor.

And Diana Woods, his new patient (who arrives late, and charmingly neurotic, in the person of Trish Van Devere) -- we suspect that she, too, is somehow involved in international espionage. Is she the hit-woman sent to kill Dr. Browning and abscond with the secret something? Could she be Nadia, the East German Mata Hari? Anagram fanciers can't help thinking she could.

Before long, it need hardly be said, sex enters the doctor-patient relationship. There is talk of marriage. And children. At which point, Dr. Browning puts his foot down. He already has an ex-wife and two children, he protests, and "Daddy is pooped!"

But their romance survives and flowers, while he continues searching for her true identity, and she continues to come up with a new fiction to cover every lie. It is all vaguely reminiscent of "The Maltese Falcon" (minus the falcon).Scott even gets to say, a la Bogart to Mary Astor, "You're good -- you're very good."

Alas, Van Devere has not yet achieved any of Astor's iceberg-like mystery. The one-tenth of her that is above sea level is the only tenth that exists in the production at this stage of its development. But if Van Devere's mood changes lack drama -- if her entire performance is simply too mechanical -- these are problems that begin in the script. The exposition and indeed the entire first act of "Tricks of the Trade" are witty and engaging, but the double-agent shenanigans that pass for a plot as the second act gets cooking are incredible, insufferable, interminable, and every other adjective beginning with "in-" in our humble language. By the time the final curtain is ready to fall, no one except the die-hardest spy-story fans could possibly care if Diana is Diana, Nadia or Lydia the tattooed lady.