LONDON — It begins with the scene that ended the final book.

Right now, we know little more about “Harry Potter and the Cursed Child,” the breathlessly awaited new play that — to the joy of fans worldwide — promises an eighth installment of J. K. Rowling’s Harry Potter saga. Set 19 years after Harry has defeated his nemesis, Voldemort, in “Harry Potter and the Deathly Hallows,” the play gives us a 30-something Harry and centers on his son, Albus Potter, entering his first year at Hogwarts just as Harry did at the start of the series.

The play, which has a story line by Ms. Rowling, Jack Thorne and John Tiffany, begins previews at the Palace Theater here on Tuesday, and everything about the production has been shrouded in tantalizing secrecy. A few details — wand design, the stitching on a cloak, cast photos — were revealed to excited fans on Pottermore.com, Ms. Rowling’s website. Even these tidbits received a level of online speculation and enthusiasm worthy of a major political event.

“None of us, all quite experienced in the theater world, have ever experienced anything of this magnitude and intensity before,” said Colin Callender, who with Sonia Friedman has produced the show, which is composed of two parts that can be viewed together or on separate days. Mr. Callender was speaking during a round-table conversation on Thursday. With him were Ms. Friedman; Mr. Thorne, who wrote the play; Mr. Tiffany, its director; Jamie Parker, who plays Harry; and Noma Dumezweni, who plays Hermione. Here are edited excerpts from their conversation about everything but the plot.

Why a play? Was it J. K. Rowling’s idea?

Sonia Friedman It was absolutely Colin’s and my idea. We knew that many other producers had approached her and she had rejected their pitches. But that’s because they were all ideas about musicals or arena spectacles. We went to her with the simple idea of a straight play. We were clear we didn’t want to adapt a novel, and we suggested exploring how Harry, an orphan, would cope as an adult and a parent.