Amy Adams is an avowed dog person. In Nightbitch, she’s also a dog-person. The new Marielle Heller film, set to premiere at this year’s Toronto International Film Festival, follows Adams’s unnamed suburban housewife—Heller’s screenplay, like the 2021 Rachel Yoder novel on which it’s based, refers to the character only as “Mother”—as her tedious, toddler-centered life goes in mysterious new directions. She starts sprouting hair in strange places; she develops a weirdly heightened sense of smell. It’s a metaphor for the transformative aspects of motherhood and perimenopause—but also, Mother seems quite literally to be turning into an animal.

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“It was so unique and otherworldly, and like nothing I’d ever read before,” says Adams of Yoder’s novel, which the six-time Oscar nominee poured through before it had even been published. Adams’s production company partnered with Annapurna Pictures to option the rights to the book—which thrilled Yoder, though she also found it slightly baffling. “It never crossed my mind,” the author says, that someone could make a film version of Nightbitch. “It’s so internal. I think it’s a huge challenge.”

But when Heller came on board, everything started to click into place. “When we thought about dream directors, Mari was our first choice,” Adams says. The only potential speed bump—Heller had recently given birth to her second child, and Adams wasn’t sure that the director of Can You Ever Forgive Me? would be ready to take on a new project—wound up becoming a major asset to the film.

“I was writing it after being isolated in my house for a year” during the pandemic, Heller says. “And my husband”—director and Lonely Island member Jorma Taccone—“was on production, so I was alone with two kids for the first time. It was a nightmare. I was sleep-deprived; I couldn’t see anybody or do anything. And my daughter was waking up at five in the morning every day.” She completed the script in fits and starts, working while her six-month-old napped and her school-aged son binged Octonauts. “I felt super guilty. I was putting my kid in front of the TV for two hours, but I needed to do it in order to get the writing done. I would literally be midscene, and someone would start crying and I’d have to stop.”

That fog-of-war perspective is palpable at the beginning of Nightbitch, as Mother stumbles through endless repetitive days with her (also nameless) toddler son. Her husband (Scoot McNairy) travels frequently for work, leaving her solely responsible for the kid’s meals, trips to the playground, and the countless readings of Goodnight, Goodnight, Construction Site he demands at bedtime. (“There’s details like that where I just put my own life into this story entirely,” Heller laughs.)

This isn’t a movie about how parenting will ruin your life. But it does tap deeply into how monotonous it can be to care for a small child—especially for someone like Mother, who was an ambitious visual artist before she and her husband left an unspecified city for an even more anonymous suburb. As a woman whose personhood has been reduced entirely to the role she plays in her son’s life, she finds herself not only bored but adrift—unable even to recall a time when there was more to her than potty training and camping out to watch the garbage truck roll by. The irony is that she chose this life, actively deciding not to put her son in childcare because she can’t stand the thought of being apart from him.

“I am stuck inside a prison of my own creation,” she imagines herself telling an acquaintance in a passage from the novel that appears largely intact in the film. “I am angry all the time. I would like one day to direct my own artwork toward a critique of these modern-day systems that articulates all this, but my brain no longer functions as it did before the baby, and I am really dumb now.”

“The thing I really attached to is this idea of loss of identity,” Adams says. Heller, too, could relate on several levels: “I have this memory of having food poisoning when my son was really little. I was throwing up, and he toddled in and started nursing on me while I was lying on the bathroom floor.” She felt emptied, “like I had nothing left. Just like, ‘My body is not my own anymore. This is so fucked up.’” At the same time, she couldn’t imagine delegating his care to another person. “It felt like I was a bear and I had this cub, and the cub wasn’t supposed to go very far away from me. I needed to be connected physically to him at all times.”

As she flounders, Mother starts to notice those inexplicable physical changes. Fur appears on her back and butt. (As her adorable son, played by Arleigh and Emmett Snowden, helpfully informs her: “Mama fuzzy.”) Neighborhood dogs start turning up wherever she goes. There’s a bump at the base of her spine that just might be a nascent tail. Things head in an increasingly surreal direction, showing just how wild Yoder let her imagination run when she wrote the novel in a sort of fevered haze. (Like Heller, she had to do it in short, focused bursts while her young son was in day care.) “One of the real challenges of Nightbitch is, what is the tone going to be? Is it going to be funny? Is it going to be dark? Is it going to be horror?” Yoder says. “This is a character who’s in emotional turmoil, but this is also an absurd situation.”

Heller settled on a film that she’s calling a comedy for women, and a horror movie for men. But really, Nightbitch hits all those notes at once, blending sharp dialogue with improvised chaos—a necessity when your film’s second-most important character is played by rambunctious three-year-old twins—and moments of graphic body horror.

Nightbitch’s ickier scenes came naturally to Heller. As a kid, the filmmaker says, “I was always trying to pop my brother’s zits.” Adams also had to go all in, donning doglike extra nipples and shooting a violent scene involving a cat that will not please PETA. (“Oh, we don’t know what happened [to the cat],” the actor deadpans when asked about it. “It could have been any number of things.”)

There’s no trace of vanity to be found in her performance. “It felt so organic, because there’s many a day where I look at myself and I’m like, ‘Well, that’s new. What’s that?’” she says. “It just sort of became an extension of the way our bodies evolve as we go through different metamorphoses, be it childbirth or aging.” Heller appreciated how game Adams was: “She was this gorgeous movie star who was never allowed to look real, and she got to look real.” Contrary to what some voices online would have you believe, Adams is not wearing prosthetics in Nightbitch—at least, not beyond the nipples and tail. “I wasn’t judging anything as it was going on,” Adams says. “I wasn’t judging my physical appearance. I was just in the character so much. So, yeah, I suppose that can feel liberating at times, but also terrifying.”

The twist in Nightbitch, in so much as there’s a twist, is that going canine makes Mother a better mother. She’s less stressed, more instinctual. Finding her footing as a parent also allows her to make art again. As Adams puts it, “through her parenting—through her mothering—she got in touch with something bigger and something primal.” It’s easy for Heller to place the film on a continuum with the first project she both wrote and directed, the 2015 Sundance sensation Diary of a Teenage Girl. In that movie, she says, “I wanted to capture how it truly felt when I had been a teenager. With this, I’m like, ‘Becoming a parent is also a coming of age.’ Your identity shifts in a really major way that not everybody talks about, especially as an artist—what you’re giving up, what you’re leaving behind.”

For Heller, making the film felt a lot like going on her own journey of self-discovery. “Part of my Nightbitch era has been just being a little bit more honest about my own needs,” she says. And being honest about the emotions coursing through her own art. “Sometimes, when people ask me what the movie is about, I’m like, ‘It’s about motherhood and rage.’ And you either get that or you don’t.”

At times, Heller’s script felt so potent that it almost frightened her. She remembers writing one line in particular that hit like an electric current: “I almost erased it three times. And then a girlfriend of mine was, like, ‘No, no, that’s everything. That is so right.’” Others were real enough to strike a nerve with her husband. “There were a few scenes where he read the pages and he was, like, ‘Okay, fuck you. Don’t put that in.’” She didn’t take them out.

Nightbitch will be released in US theaters by Searchlight on December 6. This feature is part of Awards Insider’s exclusive fall film coverage, featuring first looks and in-depth interviews with some of this coming season’s biggest contenders.