PARIS  From Monteverdi’s “Orfeo” through Wagner’s “Ring” cycle, the supernatural has been a constant in opera, an art form that more than most thrives on the suspension of disbelief. In that sense the idea of an opera inspired by David Cronenberg’s science-fiction horror film “The Fly” fits comfortably into the mold.

With “The Fly,” Howard Shore has written his first opera after decades as a composer for screen blockbusters like “The Lord of the Rings.” To Mr. Shore the film had a crucial ingredient for opera: an ill-fated love triangle. It was a story he knew all too well, having written the score of the 1986 film version too.

“I always thought it to be a classical opera theme,” he said, “a great story of love and death, of true love that survives physical decay and the ultimate sacrifice.”

But to translate Mr. Cronenberg’s movie into opera meant starting afresh. The English-language libretto, by the playwright David Henry Hwang, adds solos, duets and choruses to the man-becomes-fly plot and borrows the idea of a flashback from George Langelaan’s short story of the same title (also the basis for a 1958 film). At the same time, unlike the music Mr. Shore wrote for the film, his opera score is now called on to drive the entire drama.