The opera Dead Man Walking more than lives up to all its promises. At the world premiere October 7 at the War Memorial, everyone in the theater felt that we were seeing and hearing one of the most thrilling and most important achievements in San Francisco Opera’s 78-year history.

Based on the book by Sister Helen Prejean (who was present at the opening) about her soul-searing ministry to a comdemned murderer on death row in Louisiana, the opera is the first by 39-year old Jake Heggie of San Francisco. For years he has been composing beautiful songs, some of which are performed by major artists on his CD The Faces of Love. His opera is full of songs and poignantly lovely melodies as well as duets, ensembles, choruses, and powerful orchestral writing. It is unquestionably a contemporary work but there is none of the dissonant shrieking that characterizes other modern operas.

DMW the opera has to me more immediacy and impact than the Tim Robbins movie, which starred Sean Penn and Susan Sarandon, who won an Oscar for her portrayal of Sister Helen, but it is not a book or movie set to music: it is a completely new work crafted supremely well for singers and structured for the stage, assisted by Michael Yeargan’s dramatically revolving sets and Jennifer Tipton’s suggestive lighting.

The libretto is by Terrence McNally, lifelong opera-lover and award-winning playwright who also wrote the book of Ragtime. Each word is vital to the action and delineates the characters: it is apparent that Heggie and McNally shared a vision and embodied it in every moment of their opera. In Heggie’s music are echoes of ragtime, blues, jazz, gospel, even of Debussy and Verdi, but the songlike arias, the strength and propulsion and rich orchestration are his own.

Patrick Summers, SFOpera’s principal guest conductor and Houston Grand Opera’s music director, was involved in the evolution of this opera and gives it his finest, most sensitive leadership.

Susan Graham as Sister Helen is stunning in the extraordinary range of emotion she projects and in her glorious singing. Frederica von Stade conveys deep involvement in the role of the prisoner’s mother. Baritone John Packard as Joseph De Rocher, the condemned man, has a fine voice, a wiry physique -- he does more pushups onstage than any other opera singer ever has -- menacing bad-boy toughness, but also at the end, vulnerability.

SFOpera’s retiring general director Lotfi Mansouri deserves credit for his faith in Heggie and for putting together this superb production: every single singer is first-rate and Ian Robertson’ choruses -- men’s women’s and children’s -- are excellent.