Paul Feig’s latest film, “A Simple Favor,” is hard to categorize. 

One part suburban noir, one part dramatic thriller, the film follows the evolution of the unlikeliest of friendships before shifting into a murder-mystery whodunit. Somehow, it also manages to be funny.

“It’s not a joke-fest, this movie, but it’s behaviorally very funny,” said Feig, known for directing comedy blockbusters including “Bridesmaids” and “Spy,” at his Feigco offices. “For me, all the humor comes from the extreme emotions or extreme personality traits of the characters and the situation they’re in.”

In “A Simple Favor,” now playing in wide release, Anna Kendrick stars as Stephanie, a widowed suburban mommy blogger who stumbles into a friendship with Emily (Blake Lively), a glamorous working mom who regularly picks up her son from elementary school while decked out in couture. The women couldn’t be more different, but the friendship is believable: Each has a trait the other lacks … and can exploit.

“It’s a heightened relationship,” said Kendrick. “There’s something about having a person in your life who, on paper, is just so different from you. You can learn so much from each other and help each other out because you have such different world views.”

The story, based on a novel by Darcey Bell, had been floating around Hollywood. After a brief bidding war, 20th Century Fox won the rights to the book in January 2016 and brought on “American Horror Story” writer Jessica Sharzer to adapt the script. It was then sent to Feigco Entertainment to produce.

“They said, ‘It’s a thriller, but it’s crazy, but it seems funny, but it’s also really dark. You do comedy, maybe you can figure this out,’” Feig remembered. “I read it and I was like, ‘I have to direct this.’”

Feig had been looking for a “Hitchcockian thriller” for a while, he says, “so I just saw the opportunity for it.”

“I never felt as a writer that I could write one of these from scratch,” said Feig, who added more twists with Sharzer to the final version. “So getting this great material and then to play with it, I was on board.”

Neither Feig nor Kendrick had read Bell’s novel before signing on for the film. In fact, Kendrick didn’t even know Feig was attached to the project until she re-read the script for a second time.

“I’m lazy and I don’t read the cover letters,” she explained. “So I read it thinking, ‘OK, this is a thriller and a mystery.’”

However, she quickly realized that it was much more nuanced than that.

“The entire time I was reading it, I was thinking, ‘Do they know that this is funny? Is it supposed to be funny?’” she said. “I was a little worried about it being (done by) a director with no experience or interest in comedy and therefore some of the situations and dialogue feeling too absurd. And then I saw that Paul was doing it and I was like, ‘Got it. On board. Into it. So excited.’

“I’m glad that I got to experience it as a straight thriller and then read it the second time knowing ‘OK, we’re going to be having some fun,’” she added. “Not going for laughs and not telling jokes but we’re going to be enjoying how absurd some of this stuff is.”

Kendrick’s preparation for playing Stephanie, a picture-perfect mom with a fair share of skeletons in her closet, included going “down a rabbit hole” of mommy blogs.

“The ones that I liked the most were really raw and makeshift, someone propping their phone up against the side of the table and just being really honest about maybe the guilt they feel as a mom and the ways they’re stressed,” she said. “But the ones that were popular were the ones that were very polished and very well-lit — the person had designed a background that they always filmed against — and there was almost something really sinister about them.

“Paul had this idea for Stephanie to talk directly to (the camera) to address the moms that are watching, which is just so overproduced and so alienating. But it speaks to how tightly wound she is, because she’s hiding so much and she’s repressing so much. It’s one of those things where, you’ve been through some trauma and you feel like as long as you just keep everything perfectly in order … everything will be fine and you don’t have to deal with the fact that you’re also a person that has this history that’s kind of dark.”

“Stephanie’s such an A student,” Feig agreed. “She’s covering up this dark history she has by dressing really bright and fun and goofy. There’s just something so nice about the contrast between what people think they’re hiding (and how they present themselves).”

“I think it’s kind of this beautiful metaphor for peeling back the layers of who someone is,” Kendrick added. “In this movie, Emily has more literal secrets, but Stephanie has a lot of tricks up her sleeve that people who know her don’t expect from her. The entire community thinks they have her figured out, and it’s nice to have a mystery as a backdrop via which to peel back the layers of her personality.”

Peeling back layers to reach something unexpected was something the director and star were interested in achieving with “A Simple Favor.” The trailer declares the film to be “from the darker side of Paul Feig,” something the traditionally comedic filmmaker was excited to pursue.

“I’m a huge fan of thrillers,” said Feig. “It’s kind of my favorite genre. I mean, if you look at all my movies, they’re all genre movies, really. The thriller was the genre I haven’t gotten to do yet but I was dying to do.

“I was really hung up on wanting it to be suburban noir. So it’s not scary things happening in the shadows, it’s happening in broad daylight. There’s hardly any night scenes in it because I just liked the idea of things happening during the day. So it was this very nonthreatening-looking environment and then really (messed up) stuff is happening in it.”

If you go

A SIMPLE FAVOR

R, 117 minutes

Playing at Niantic, Mystic Luxury Cinemas, Waterford, Westbrook, Lisbon