The Olney Theater's production of Ronald Harwood's "The Dresser" owes much of its naked power to David Cromwell who plays a servant jealously devoted to an aging Shakespearean actor. The part might have been tailored for him on Saville Row.

But the role of histrionic tragedian is at least a size too large for Bernard Frawley. He seems too much the common whiner -- with an Irish inflection to boot -- to be the zajestic megalomaniac nicknamed "Sir."

The drama, nevertheless, is rich and well- crafted, and the cast is generally strong enough to make the show worth the trip.

Harwood's script, treating a touring Shakespearean troupe in the provinces of England during the Blitz, focuses on the symbiosis between Sir and his dresser Norman. The two acts take place on a night blaring with air-raid sirens, when the star, delirious and spent from too many performances in too many hamlets, is scheduled to portray the heroically mad Lear.

The old actor, addled but still impressive, at first refuses to go on: "I want a tranquil senility," he says in a lucid moment. The servant flatters, cajoles and badgers; the master preens, resists and cowers. The question of who is servant and who master is the play's central refrain -- and would have been more tantalizing if the actor playing Sir had more stature.

Around Sir revolve lesser lights of the theater company: Madge, the stage manager who loves him unrequitedly; Irene, the ingenue who excites his lust; Her Ladyship, the common-law wife who hopes in vain for a proper wedding; and Oxenby, a dour newcomer who wants Sir's exalted position.

Cromwell portrays Norman the dresser as touchingly loyal, jumping up to give his master a massage, skipping like a spright to bring him tea. He's also a tyrant, though: sulking and even shouting to work his will.

Brandishing a knife when the occasion demands, Norman protects Sir from all enemies and vanquishes all rivals, even when it no longer matters. THE DRESSER -- At the Olney through July 24.