VERDICT -- At the Olney through June 28.

Much of the fun in seeing a play by Agatha Christie, as in reading one of her novels, comes from second-guessing the author at every turn. As the crime unfolds, would-be snoops can ask, What's to be done?, To whom?, Why?, How? and, finally, Whodunit?

"Verdict," a Christie offering now at the Olney Theater, becomes something of a game of 20 Questions before the final curtain falls. The play doesn't tell you much about the human condition, and it strains credulity at times, but it's enormous fun.

The plot, of which it's best to say little, concerns a starry-eyed professor, his invalid wife, his beautiful young pupil and his equally appealing assistant, all in London, circa 1958. For laughs, there's a busybody housekeeper with a Cockney burr. There is romance, and melodrama. Oh yes, there is also foul murder.

The fingerprints are unmistakably Agatha's:

Professor Karl Hendryk, a refugee from the Communist bloc, bristling with indignation at the wealthy Sir William Rollander when the latter offers him the world if only he will take on young Helen Rollander for a private tutorial. "Bribery and corruption!" rails the professor, who suspects that Helen wants to study love, not philosophy. "Oh, yes," the rich man agrees with a smile. "Just as you say. Bribery and corruption."

In another deft touch, the loudmouthed Mrs. Roper, Hendryk's housekeeper, assures his wheelchair-bound wife that she will get well: "Of course you will, dearie. Of course you will. Never say die!"

Marlene Bryan, a native Britisher who plays the frumpish Mrs. Roper, is so intrusive, domineering and gauche in the role -- in the best tradition of Christie servants -- that you may just want to leap on stage to shut her up. A mixed pleasure to watch, she steals every scene in which she appears.

The Olney's classy production, acted by journeymen and directed with confidence by Leo Brady, moves like a sleek yacht making for Marseilles.