It is not wholly inaccurate to describe George Bernard Shaw's "Candida" as a sex comedy, if you bear in mind that the old devil had somewhat cerebral notions of sex.

We are talking, after all, about a play built on a variation of the eternal triangle -- the slightly smug and ever-so-moralistic husband (the Rev. Morell); his gracious, decidedly alluring wife (Candida); and the impetuous 18-year-old poet (Marchbanks) who tries to alienate her affections.

The action may be set in a church rectory and the characters may be considerably more articulate about the tumultuous states of their souls than those in, say, "Right Bed, Wrong Husband," but what keeps the play spinning along is the possibility of hanky-panky ripening on the horizon.

In the generally spirited revival of the play that opened Tuesday night at Olney Theatre, only one of the three major characters is really properly cast. But it's the crucial one -- Candida, herself. She is played by Barbara Andres, a handsome actress who seems born to wear the pinch-waisted finery and the Gibson Girl hair styles of the late 19th century.

There is something warmly maternal about Andres -- an enveloping fullness of figure and manner. One easily can picture her dispensing tea and sympathy. But there is also something tantalizing about her, a graceful independence that keeps her just out of arm's reach. She is, in short, a creature worth battling over -- which is precisely what Shaw's men are doing for three acts.

As the summer season goes at Olney -- and it's not gone all that well so far -- "Candida" is a notch up. The production is pleasant to look at (although I swear I've seen Joseph St. Germain's paneled drawing room set on Olney's stage before).

Director Leo Brady has brought a certain alacrity to the proceedings, always a wise tactic with Shaw, who does love to hear himself talk. And the ranks of the supporting cast have been wisely filled with Terrence Currier, decked out in lamb chops and a pot belly, as Candida's scoundrel of a father; by Joseph P. Normile, as the Rev. Morell's assistant, a chipper eager-beaver; and, to a lesser degree, by Debra Cerutti, as the reverend's pent-up secretary, who, with two glasses of champagne under her belt, will momentarily shed her stern sense of duty.

What this production doesn't get quite right, however, are the two rivals for Candida's comforting hand. On the surface of things, the Rev. Morell is solidly ensconced in his marriage and firmly committed to his mission of bringing spiritual truth and socialist rhetoric to the masses. A bulwark of middle age, he can, from all stolid appearances, take care of himself perfectly well, thank you.

Marchbanks, on the other hand, is a sniveling whelp, as disheveled of soul as he is of wardrobe. Drunk on the poetry but otherwise plainly undernourished, skittering from table to chair like a frightened field mouse, he is, as he himself puts it, "a wretched little nervous disease." If you were to pit him against Morell, there should be no question of which one would carry the fray. Or to put it another way, when Candida decides in her infinite wisdom that she will give herself "to the weaker of the two," the audience should automatically look to Marchbanks. It doesn't work out that way at Olney.

Although Bernie McInerney gives a reasonably assured performance as Morell, he is a slight man, and his pale features are more esthetic than not. By the same token, Michael Rothhaar can't entirely overcome the impression that his Marchbanks is actually a rather robust creature at heart, spitting with the energy of good health. When McInerney glowers, you're not entirely convinced. No more so than when Marchbanks cowers. The necessary distinctions between the two are blurred.

If Shaw calls for two seemingly unequal rivals, a poet and a preacher diametrically opposed in tone and temperament, it's for a good reason. The sly dog relishes nothing so much as a good paradox and he has a last-act trick up his sleeve. In a final showdown, he turns his men inside out. The true weakness lies not in the tremulous person of Marchbanks, and the strapping confidence of Morell proves to be a bit of a sham. If the play is to work its full measure of charm and surprise, however, we must be taken in beforehand by appearances. To sense the frailty in Morell or the spunk in Marchbanks before Shaw wants us to is to beat the play to the punch.

As matters stand at Olney, we are taken in mainly by Andres, who lends strong support to Shaw's life-long conviction that women are really the superior sex. A production of "Candida" with a seductive Candida as its chief virtue may not be everything. But it's something. Enough, at any rate, to keep this revival buoyant and attractive.

CANDIDA. By George Bernard Shaw. Directed by Leo Brady; sets and lighting, Joseph St. Germain; costumes, Gwyn Shopland; With Barbara Andres, Bernie McInerney, Michael Rothhaar. Terrence Currier, Debra Cerruti, Joseph P. Normile. At Olney Theatre through Aug. 29.