Fall, Huntington Theatre Company at Wimberly Theatre, Calderwood Pavilion, Boston Center for the Arts, South End, through June 16. 617-266-0800, 617-933-8600 or bostontheatrescene.com

Attention needed to be paid to Daniel Miller. After all, his father was Arthur Miller, who invested such seminal works as "Death of a Salesman" and "All My Sons" with great moral urgency. Miller's singular stage sensitivity to the complex relationships of fathers and sons makes his own failings regarding a son with Down syndrome all the more disturbing.

Now Huntington Theatre Company is giving the untold story of the great American dramatist's secret parentage must-see attention in the Huntington Theatre Company's riveting Calderwood Pavilion world premiere of the Bernard Weinraub play "Fall" (seen in a late preview).

Unlike Miller's Marilyn Monroe-inspired drama "After the Fall," former New York Times journalist (with Hollywood as his beat for many years) Weinraub does not employ fictional names for playwright Miller, Austrian photographer wife Inge Morath, their son Daniel and legendary producer Robert Whitehead.

The one exception is fictionalized obstetrician Dr. Paula Wise, whose counseling in the play about 1966 -born Daniel reflects the evolution of medical approaches to Down syndrome and its treatment. Curiously, Weinraub refers to daughter Rebecca Miller-who is married to the gifted actor Daniel Day Lewis (the male lead in a film of Miller's "The Crucible")-but does not include her in the cast of characters. Rebecca has claimed that her father had feeling for Daniel, actually wept and did visit him. Still, as the play accurately indicates, neither Miller nor Morath's Times obituary mentions Daniel, and the playwright did not include him in his 1987 autobiography.

If Morath seems to come off as more concerned about their son, "Fall" does nevertheless point to the difficulties both Arthur and Inge faced at a time when medical authorities were advising parents to send a Down syndrome child to an institution. Theatergoers may have to decide for themselves whether the playwright has employed too much dramatic license in constructing the parents' exchanges about their feelings and in demonstrating their differing involvements with Daniel.

At the same time, Weinraub-who wrote the incisive 2007 Drama Desk nominee "The Accomplice" (seen Off-Broadway by this critic) that deals with the failure of FDR's administration to save Jews trying to flee the Nazis-does build a journalistic contrast between public activist Miller and parent Miller. Miller is seen concerned with Whitehead about the Broadway staging "After the Fall" and strongly committed to the anti-Vietnam War movement. In key moments, though, he seems unable to give top priority to the needs of his son.

With a strong cast, Huntington artistic director Peter DuBois smoothly captures the differences between Miller the celebrated playwright and activist and Miller the flawed parent. Josh Stamberg captures Miller's public confidence and his private inner conflict. Joanne Kelly, in the premiere's best performance, finds all of Morath's inner strength as well as her angst-especially after she and Arthur learn of the unspeakable abuse at the training school to which Daniel was transferred at age four. John Hickok is properly warm and wise as Whitehead. Joanna Glushak evokes liberal Dr. Wise's earnest intentions and the best comic lines at moments of perspective-best of all, her assertion as the mother of a Republic son that no one could be worse than Bush.

Nolan James Tierce, an actor with Down's syndrome himself, has all of Daniel's radiant dignity. Brandon McNeel's smart scenic design ranges from hospital and office simplicity in the first act to spacious elegance at the Miller's Roxbury, Connecticut home in the second. Zachary Borovay's sharp projection design handily illustrates the play's half-century timing-1964-2005

Ultimately, Miller will stand as a great American playwright whose major works remain powerful moral statements. Nevertheless, Weinraub's provocative play points to the complexity of Miller's personal life. Most importantly, "Fall" calls needed attention to Down syndrome children and their improving lives, longevity and achievements.