By JANET MASLIN, April 30 1999

David Mamet's handsome, stately adaptation of Terence Rattigan's play "The Winslow Boy" does not embellish upon its source material. Instead it skillfully pares the play down to its essentials, arriving at a faithful but tighter version of this drama about a family defending the honor of its young son. Especially notable for their absence are Rattigan's stage directions about the characters' emotions, the ones specifying when anger or relief, humility or confidence is an appropriate reaction. Mamet likes his principals trickier than that.

While "The Winslow Boy" affords no gamesmanship on a par with other Mamet films like "The Spanish Prisoner," it works as a precisely calibrated war of nerves in which truth and deceit are all-important. Rattigan's 1946 play was based on the 1910 trial of George Archer-Shee, a 13-year-old cadet at the Osborne Naval Academy who was accused of stealing a five-shilling postal order. The boy's father, a Liverpool bank manager, went to enormous lengths to argue his son's case in what became a cause celebre. The family enlisted the barrister who had prosecuted Oscar Wilde in a notorious libel suit.

The film's deliberate reserve makes the nuances of this situation especially delicate. It is set in motion when the schoolboy Ronnie Winslow (Guy Edwards) returns home unexpectedly -- the mysterious curtain-raising event for Rattigan, and one that Mamet manipulates with greater suspense. By the time Ronnie arrives, the rest of his family has been introduced: cigarette-smoking suffragist sister Catherine (Rebecca Pidgeon), wayward brother Dickie (Matthew Pidgeon), refined mother (Gemma Jones) and stern patriarch (Nigel Hawthorne). Another Mamet touch is giving the father, Arthur Winslow, a casual opening reference to the biblical dream of seven fat years followed by seven lean ones.

The Winslows' lean years begin when Ronnie arrives, reveals the theft and is asked by his father whether he is guilty. The inquiry is staged with enough cool understatement to lend a shade of ambiguity to Ronnie's denial, and to the family maneuverings that follow. By keeping his expert cast so carefully in check, Mamet trades in the possibility of high drama for a more quietly piercing approach. As the Winslows grow determined to defend Ronnie at all costs, the film fosters tension without ever making a histrionic move.

As in "The Spanish Prisoner," the defiantly arch acting style of the filmmaker's wife, Ms. Pidgeon, is central to the overall tone. Ms. Pidgeon defines the film's eccentricity by ignoring the conventional aspects of a character (a young woman with strong ideals and several different suitors) who might well have been played in more heated fashion. Instead, she spars dryly with the story's many male characters, not least of them Jeremy Northam as the famed barrister who deigns to take Ronnie's case. Her prickly manner once again risks throwing audiences off balance. Nonetheless, she bristles most effectively and plays Catherine with strong presence and a sharp, lucid edge.

Hawthorne, in a wonderful performance, inhabits the role of Arthur Winslow with wry urbanity and stirring conviction, fully capturing the weight of what the Winslows endure. The case brings financial hardship, alters what was once Catherine's putatively bright future, and rocks everyone's confidence in law, justice and royal authority. Arthur handles all of this with an Edwardian dignity that is heightened by the film's own brand of reserve: keeping the events of the case and the public clamor it causes at a deliberate remove, Mamet compresses vital plot developments into glimpses of headlines and editorial cartoons, and lets major news arrive almost casually from the family's memorable maid (Sarah Flind).

"The Winslow Boy" is photographed, with a deliberate debt to John Singer Sargent's composition and lighting, by Benoit Delhomme, whose work on "The Scent of Green Papaya," "Cyclo" and the forthcoming "Loss of Sexual Innocence" is striking for its radiant beauty. Though tethered to the past, it is mindful of the present-day implications of its story. A scene in which a reporter visits the Winslow home and casually demolishes their privacy is artfully staged, carefully balanced, and fresh as ever.