A Sherlock with 20th-century touches. A bravura performance from Langella as Baker Street sleuth

Sherlock's Last Case Play by Charles Marowitz. Directed by A.J. Antoon. Starring Frank Langella, Donal Donnelly.

``If Holmes is the victim, who will solve the crime?''

Who indeed?

Not to worry. The question (posed in a television commercial) receives a spine-tingling answer in ``Sherlock's Last Case,'' by Charles Marowitz.

For starters, the new neo-traditional thriller at the Nederlander Theatre stars coproducer Frank Langella as the legendary Baker Street sleuth and Donal Donnelly as an untraditional Doctor Watson.

``Sherlock's Last Case'' opens on a fitfully stormy night in the pleasantly cluttered quarters of Holmes and Watson. The walls are festooned (by designer David Jenkins) with exotic and slightly sinister knickknacks, surmounted by a portrait of the queen herself.

Holmes and Watson soon become preoccupied with a piece of threatening doggerel, purportedly from Simeon Moriarty, the surviving son of Professor Moriarty, Holmes's late nemesis. The communication is followed by the arrival of an attractive young woman who identifies herself as Liza Moriarty (Melinda Mullins) and launches into a recital that fascinates Holmes and proves something of a tour de force for Miss Mullins.

From this point on, the unfoldment of ``Sherlock's Last Case'' must be left to Mr. Marowitz and the savvy cast directed by A.J. Antoon. Some facts may be disclosed without giving away the plot. The faithful Mrs. Hudson (Jennie Ventriss) journeys to Scotland to visit an ailing relative and is thereby sidelined from most of the horrendous plot.

Dr. Watson receives a knighthood. Besides proving once more a master of impersonation, Holmes displays an interest in Liza uncharacteristic of that pronounced misogynist.

Playwright Marowitz applies what amounts to a 20th-century parodist's view to Sir Arthur Conan Doyle's 19th-century characters. Holmes salts his customary haughtiness of speech and manner with an occasional naughtiness. He is more than usually peremptory with Watson and downright nasty to Mrs. Hudson. Furthermore, ``Sherlock's Last Case'' upgrades the good doctor in the scheme of things. Watson's surprising behavior springs from the hurts and indignities he has suffered as a result of Holmes's acidulous condescension.

Such are the quirkily modernist ways in which Marowitz seeks to endow ``Sherlock's Last Case'' with elements of the psychological comedy melodrama. Yet such extensions can only go so far. The comic thriller is by its nature a wind-up toy of theaterdom. Thrillers depend on plot twists, sudden surprises, and, by no means least, on physical paraphernalia.

In the last-mentioned respect, ``Sherlock's Last Case'' triumphs nicely. A revolution of the turntable transports the action from the comforts of Baker Street to the horrors of the creepy underground cellar to which Holmes, Watson, and eventually Inspector Lestrade (Pat McNamara) are inexorably drawn.

Assisted by lighting designer Pat Collins, Mr. Jenkins has created a hermetic dungeon replete with those pseudo-chemical retorts that emit lethal vapors. Finally, ``Sherlock's Last Case'' ends on the eve of Guy Fawkes Day, when the sounds of fireworks and gunfire are indistinguishable.

``Sherlock's Last Case'' is true in its fashion to a treasure-trove of lore and source material. For those wishing an alternative to Jeremy Brett's Sherlock currently on public television and Basil Rathbone's on late-night TV reruns, Messrs. Marowitz, Langella, Donnelly, and company offer an amusingly chilling entertainment, stylishly acted, and extravagantly produced.

Besides the bravura performances by the two stars and the stalwart support by previously mentioned players, the cast at the Nederlander includes the mysterious Morris Yablonsky and Daniel M. Sillmun. Robert Morgan has costumed them all picturesquely and (on occasion) scarily and Michael Ward has composed mood-enhancing music.

But is this really Sherlock's last case? Never believe it!