“Hatching” follows Tjina (remarkable first-time actress Siiri Solalinna), a 12-year-old gymnast whose already complicated young life gets much weirder after she discovers an abandoned egg in the forest near her idyllic home. Feeling guilty — she’s fairly certain that its mother was offed by Tjina’s own maniacal mom — she takes the egg home. She cuddles it close. It grows. And grows some more, until Tjina hatches…a bird? a girl? both? In Ilja Rautsi’s original screenplay, the protagonist was a teenage boy. “[Ilja] said that he has this idea that a boy hatches a doppelganger out of an egg, and I just thought that sentence was so interesting,” Bergholm said in a recent interview with IndieWire. “I felt that it could be something that, in a really weird way, I could relate to and that I could make it my own film.”

On her first meeting with Rautsi, Bergholm offered up her big idea. “I said that I wanted [the character] to be a girl,” the director said. “There are far too few interesting and complex female characters in films. I haven’t really found many characters I can really relate to and that was the reason for that. I started to think about this [idea] that Ilia had, and I drew myself an egg and started to think about ideas around it.” For the film’s first act, Rautsi’s main character attempts to conceal the egg. Bergholm wondered: Might she be trying to hide other things, too? Emotions, changes, secrets? Who doesn’t do that as they’re growing up? Courtesy of Laura Malmivaara. An “Hatching” premiered at the 2022 virtual Sundance Film Festival, where it received stellar reviews. Currently at a very healthy 92 percent on Rotten Tomatoes, its unsettling explorations of motherhood, mother-daughter dynamics, and coming of age have drawn comparisons to classics like “Psycho” and “Rosemary’s Baby” and modern body-horror counterparts including “Black Swan,” “The Babadook,” and “Hereditary.” Despite the sense of terror that emerges as Tinja’s egg grows (and grows), Bergholm and Rautsi never wanted Tinja’s own maturation to be the scariest part of the film. “We didn’t want to tell that, ‘OK, the girl reaches puberty and then all hell breaks loose and she gets her period and then it’s so horrible,’ because it’s not that horrible,” she said. “She just happens to be in an age when she’s growing up. The real horror for her is that her mother doesn’t really accept her fully as she is.”

Bergholm is pleased with the response to her complex story and acknowledges her love of David Cronenberg, Julia Ducournau’s “Raw,” and “The Others,” but adds: “I tend to not think about other films that much when I plan the story, because I don’t want to mimic something that is already done.” Part of her success in that regard lies with her conceptualization of the egg itself. In early sketches of the creature that emerges from the egg, Bergholm instructed concept artists to cook up something that was “partly a bird, partly a girl.” (In later sequences, Solalinna plays both Tjina and her shocking charge.) She added, “I really wanted it to be, in a way, deformed, because the girl wants to be perfect, this perfect gymnast who has a perfect body. So this is something totally different, it’s all deformed and can’t even walk properly. It’s just ugly and disgusting and very thin, because there is this a hint of eating disorder in the film.” But she didn’t want it to be evil. “It’s not predatory,” Bergholm explained. “It has very big eyes, so it’s like a thing or a child that is all instincts, open, and wants to be loved, even though it’s so disgusting. I said it’s like a smelly teenager who is raging to his parents and still wants to be cuddled and loved.” Courtesy of IFC Midnight. An IFC Midnight release. Bergholm knew she wanted the creature to be a puppet, because it needed to “have a physical presence.” She wanted no less than the “best possible person to make this puppet,” and sought that person in a thoroughly modern way: She Googled it. “I actually Googled ‘the best animatronic designer in the world,’ and then I found Gustav Hoegen, who has done ‘Star Wars’ and ‘Jurassic World’ and ‘Prometheus’ and so on,” she said. “So I emailed him and he got excited to come on board.” Her timing was key: Hoegen, who served as the supervising animatronics designer on the most recent trilogy of “Star Wars” films, plus spinoffs “Rogue One” and “Solo,” was in between jobs and looking for something new. “He really he wanted to build up his own company and was looking for a work in which the animatronic puppet would be the really important character,” Bergholm said. “Here, it really is one of the main characters, so he got fascinated to make the puppet.” The pair brought on two-time Oscar nominee Conor O’Sullivan, a makeup artist and prosthetics expert whose credits include “Saving Private Ryan,” “The Dark Knight” and “Game of Thrones.” The crew also built four sizes of the egg the creature hatches out of, plus multiple copies of the final egg, which is broken a number of times as part of the shoot. And the puppet? Bergholm says she still has it. Who could abandon such a treat? IFC Midnight releases “Hatching” in theaters on Friday, April 29. Sign Up: Stay on top of the latest breaking film and TV news! Sign up for our Email Newsletters here.