Writer-director Emerald Fennell’s debut feature, “Promising Young Woman,” drew an exuberant response at its premiere at the Sundance Film Festival Saturday night. The film, which will be released by Focus Features on April 17, is provocative — and will perhaps be divisive, particularly its ending. It’s a perfect talker for the #MeToo era.

It’s best for audiences to see “Promising Young Woman” cold, but the basic plot is that Carey Mulligan plays a 30-year-old woman named Cassie, who lives with her parents and works in a café. She dropped out of medical school for reasons that become clear as the plot unfolds. But what audiences see immediately is that Cassie’s side gig is going out to bars and appearing so drunk that a man will take her home — but to say what she does once they do would be a spoiler. (The movie’s tagline is “Take Her Home and Take Your Chances.”) Cassie’s vengeful calling gets complicated when she meets a charming nice guy (Bo Burnham), with whom she went to med school — again, no spoilers!

Mulligan’s performance is a masterwork: Her Cassie is brilliant and witty; she’s also sad and tragic. Through Cassie, Fennell interrogates rape culture, masculinity and its discontents, womanhood as performance, and trauma.

The supporting players are well-cast, with the winning Burnham as a potential boyfriend; Alison Brie as a malignant med school friend; Laverne Cox as Cassie’s concerned boss; and Clancy Brown and Jennifer Coolidge as her helpless parents. The movie was produced by FilmNation Entertainment and Margot Robbie’s LuckyChap Entertainment.

“Promising Young Woman” is Fennell’s first narrative feature, but she was the showrunner of Season 2 of BBC America’s “Killing Eve” last year. She has also written horror novels. She acts as well, most recently playing Camilla Parker-Bowles in Season 3 of “The Crown, and for years played Patsy on “Call the Midwife,” a lesbian character who launched a thousand YouTube tributes.

During the audience Q&A at the Marc Theatre in Park City, Fennell said she wanted to “subvert” genre films — not only rape revenge movies, but comedies also. “To love the genre,” Fennell explained, “but to subvert and undermine it. What I wanted to do was not have anything in this movie that I haven’t seen in a comedy in the last 15 years — treated very differently here.”

She answered questions about the movie’s shocking ending (no spoilers!). “What I wanted to do is look at catharsis, and why things are cathartic,” Fennell said. She asked the audience not to spoil the ending, because “if you know, it’s a very different experience.”

And as a reminder, those who attended the film received in their email inboxes “A Note From Cassie,” saying in part, “Please don’t ruin the surprise.” So get ready to talk about “Promising Young Woman” as of April 17.

But one more thing for those who have enjoyed the trailer: the strings-heavy cover of Britney Spears’ “Toxic” is indeed in the movie.