Cannes festival director Thierry Frémaux promised that this year’s Un Certain Regard sidebar lineup would be more driven by narrative and genre than years past. Looking at Charlie Polinger‘s feature directing debut “The Plague,” he wasn’t kidding.

This harrowing, 35mm-shot story of pubescent boys tormenting each other at a water polo summer camp doubles as a coming-of-age drama and an adolescent, acne-scarred body-horror nightmare. The 12- and 13-year-olds populating its frames are all afraid of catching an imagined (or not?) contagion — let’s call it puberty — that turns their brains into “mush,” one says, and manifests with psoriasis-like lesions on their bodies. But the words and almost ritualistic humiliations they exchange (think the mocking of speech impediments and centipedes thrown into your bed at night) are even more wounding.

Polinger, an AFI Conservatory grad working with many of his fellow alumni including cinematographer Steven Breckon, based this disturbing and personal film on his own experiences as a kid at an all-boys summer sports camp, culling from his rediscovered journals to write the script. Millennials who came of age in the aughts (“The Plague” is set in summer 2003) will recognize the touchstones, from the period music references to the Capri-Suns everyone seems to be slurping. “I was leaning into the Capri-Sun, into sort of this pre-internet or very early internet age, with the kind of jokes that they make,” Polinger told IndieWire.

Joel Edgerton, who stars as the boys’ generous but out-of-his-depth coach in terms of dealing with unruly and toxic boys, initially received the script from Polinger’s agent and wanted to direct it. “I was like, ‘I really have to direct this one. It’s too special to me.’ He was just really cool about it. We ended up getting on a call. He really related to the themes, the social dynamics of these kids, and bullying, and his own experiences being a 12-year-old boy in Australia. He basically just said, look, I’m happy to produce the film and act in the film, and do anything I can to help get this made.”

Polinger and his casting director Rebecca Dealy (“Hereditary”) looked at thousands of tapes of kids to cast the right ensemble. They landed on “Griffin in Summer” star Everett Blunck as Ben, the hero of this story if there is one, and the seemingly innocent kid through whose eyes we see the film. The kind of kid who will see with his awkward, ruthlessly bullied peer who’s left alone at the cafeteria. They found Kayo Martin, who plays the camp’s freckled top bully Jake who presides over the cool-kids table with imperious authority, off social media. It’s a breakout performance for a young star.

“He felt exactly like the type of bully or character who messes with your head in a way that I feel like I haven’t seen represented in a movie or TV show very often because he’s always very understated,” Polinger said. “You never know if he’s joking or not, and it really kind of gets inside your head. He is so comfortable hanging out with adults all the time and going around New York, going to all the bagel shops and all these places [where Martin does social media pranks], and he does have a certain maturity level that can actually play very uncanny in the situation with other boys.”

There are scenes in “The Plague” that pit the child actors into adult scenarios that are, in real life, likely familiar to them. In one scene, they share sexual fantasies and talk about masturbation from across each other’s bunk beds. Directing children always comes with its own set of challenges, even with parents on set, but Polinger and his team worked with an intimacy coordinator to burrow into these most uncomfortable (but relatable) moments.

“The first day with the intimacy coordinator, we all sat around and we were talking about the scene, and she was coming at it very delicately: ‘Is this something that you guys know about?’ And they were miles ahead of her in terms of what they already knew and the jokes that they were making,” Polinger said. “It was really important to me that we were capturing that age in a real way. [The actors] were very fearless and just excited to dive into it… They were so much more mature than you would imagine.”

In terms of references for the film’s more horror-leaning later stretches, Polinger wanted to combine the feel of 1980s and aughts coming-of-age teen movies with a more genre-oriented sensibility (comparisons to “Black Swan,” eventually, are invited).

“I love those movies about boys, though I often feel like a lot of movies about young boys are either a little more sort of broey hangout or a little more nostalgic, kind of biking-around-the-suburbs type of thing,” he said. Movies like Bo Burnham’s “Eighth Grade” and Julia Ducournau’s “Raw,” he said, “capture a social dread and vulnerability of your body and something you don’t see as much with boys because it requires a certain vulnerability to be an object of terror in that way… I was even looking at some sort of dread-filled, ‘Shining’ daylight kinds of horror movies, [with] huge imposing spaces.”

Movies about military situations, like Stanley Kubrick’s “Full Metal Jacket,” also came to mind. Even Claire Denis’ “Beau Travail,” which is “such an incredible exploration of masculinity.”

Every rising indie filmmaker these days wants to shoot on film — who doesn’t? — which can be a big upfront non-negotiable from a first-time director. But “The Plague” benefits from that celluloid touch, making the movie like a grainy memory of a bad dream. “It was pretty challenging. We had to find some additional funds to do it. We got a lot of help from Kodak. [It was] definitely hard, and especially with kids and pools and all the other variables that add more time, and having tight days. The film [aspect] just added a whole other wrench into it,” Polinger said, though “The Plague” did shoot during a sweltering summertime when the kid actors were out of school.

Shooting on film, though, he said, “just made it feel magical. We were capturing something that felt timeless and, to me, there’s no comparison. It looks so great to shoot on film, and these kids’ faces and closeups just rendered in such a beautiful way.”

“The Plague” will seek a distributor at Cannes, though Polinger already has wind in his sails with another movie lined up, and at A24: an adaptation of Edgar Allan Poe’s “The Masque of the Red Death” starring Sydney Sweeney. “The Plague,” which Polinger wants to be seen in theaters, would be a smart fit for any distributor looking for a risky genre offering, and one that offers no easy answers about the prickly (and, yes, pimply) perils of adolescence.

“The Plague” premieres at Cannes on Thursday, May 16. It is currently seeking U.S. distribution.