The story of "Doubt," which turns on a Catholic-school principal's determined efforts to remove a possibly pedophilic priest, hardly seems ripe for operatic treatment. The medium is less comfortable with nuns than with whores. But "Doubt," written by composer Douglas Cuomo and librettist John Patrick Shanley and unveiled Saturday at the Ordway Center as part of Minnesota Opera's 50th season, is an absorbing opera of ideas--a philosophical yet lyrical whodunit, cunningly inconclusive, that speaks to the heart. (Operagoers needn't fret: the work makes its titular abstraction as vivid as any conventional love triangle.)

The libretto is Shanley's third version of the story, set in a church school in 1964, in the working-class Bronx neighborhood where the writer grew up. First incarnated as a talky, Pulitzer- and Tony-winning play for four actors, "Doubt" then became an Oscar-nominated film, with Meryl Streep as Sister Aloysius, the starchy principal, and Philip Seymour Hoffman as Father Flynn, the suspect priest. Now it's an opera, Shanley's first. And the writer has plainly taken to the medium, tempering his native loquacity and delivering a series of expanded, poeticized moments that are grist for the composer's mill.

Cuomo's is music of quiet power, most moving when most intimate; he knows how to insinuate what cannot be spoken. Though unmistakably American in sound, with echoes of Copland, Bernstein and John Adams, he avoids both pop cliché and music-theater razzmatazz. If Cuomo's vocal lines sometimes seem awkward, his pacing is remarkably deft: the potentially tedious closing scene of Act 1, for example, which veers from a theological critique of "Frosty the Snowman" to oblique charges of impropriety, is a masterpiece of timing.

Alive to Sister Aloysius' steeliness, vulnerability and quirky humor, Christine Brewer makes her one of the most fully realized characters in contemporary opera. This is a great performance by a consummate singer; that it comes in the context of a new work makes it all the more extraordinary.

Baritone Matthew Worth, the male lead in this tenorless opera, makes us feel ambivalent about Father Flynn and makes his every syllable intelligible. As Sister James, the young nun whose tenuous innocence is shattered by the opera's end, Adriana Zabala sings with passion and compassion.

Julius Andrews, a seventh-grader from Coon Rapids, is affecting as Donald Miller, the lonely boy at the center of the action. And as Donald's mother, Denyce Graves, returning to the company 22 years after a memorable debut as Carmen, is commanding in her scene -- arguably the opera's finest -- with Brewer.

Stage director Kevin Newbury, strongly abetted by Robert Brill's columned set and Japhy Weideman's painterly lighting, actualizes the story's dramatic promise; his scene changes are pure poetry. Conductor Christopher Franklin pilots his chamber-orchestra-sized forces through Cuomo's tricky rhythms with aplomb. And the best is saved for last: a dark, riveting ending that melts into silence. I doubt that anyone breathed.