The stars of “Speak No Evil,” “Smile” and “Nanny” plumb psychological depths in very different characters.Sometimes the ordinary, the routine, the mundane can be more frightening than an arsenal of chain saws and axes. Especially when everyday interactions become uncomfortable — and maybe even threatening. This fall, a handful of outstanding performances turn what, on the surface, seem like psychological dramas into something truly terrifying. We asked the actors in “Speak No Evil” (due Friday), “Smile” (Sept. 30) and “Nanny” (Nov. 23) to discuss the transformation.Fedja van Huet, ‘Speak No Evil’“I think every person has had the same experience,” Fedja van Huet said in a video call from his home in Utrecht, the Netherlands. He was describing that universally creepy sensation when someone fails to read the cues — or chooses to ignore them — and gets a little too close. “I had it with the father of a girlfriend of my daughter. And I said, ‘Why do I feel so awful? Because somebody went over your boundaries.’”There’s a lot of overstepping in “Speak No Evil,” Christian Tafdrup’s terrifying dissection of social conventions, starring van Huet as Patrick, an electrifying Dutch tourist in Italy who, with his wife, Karin (Karina Smulders, van Huet’s real-life wife), seduces an all-too-polite Danish couple, Bjorn (Morten Burian) and Louise (Sidsel Siem Koch), onto a hell ride.The Tuscan sun seems to rise and set in Patrick when we first meet him, with Bjorn captivated by his easy magnetism.But when Patrick and Karin invite the Danish couple and their daughter to Holland, Louise has misgivings whereas Bjorn is tempted. After all, what’s the worst that can happen?That’s when the squirming begins.Patrick provokes the well-mannered Danes, who leave but then return — perhaps he’s simply eccentric — despite every cell in Louise’s body screaming, “Run!” Then there’s Patrick and Karin’s peculiarly silent son.“Speak No Evil” is the first horror film for van Huet, who was still in drama school when he was cast as the lead in “Character,” which won the 1998 Oscar for best foreign language film. He is now shooting an Amazon series based on a young adult novel. That he’s the bad guy is all he would reveal.“I’m one of the usual suspects in Holland; I’ve been blessed with a lot of work,” van Huet, 49, said. And yet he and Tafdrup had never collaborated before. “You don’t have any thoughts before because you don’t know each other. So that’s fresh. That’s interesting.”The night before auditioning for Patrick, van Huet read the script and realized that “Speak No Evil” was no mere psychological drama.“I was a little upset, actually,” he said, laughing.And while he sometimes had the urge to go sinister with his eyes — he raised an eyebrow ever so slightly, transforming his face from one you could trust into one not so much — Smulders had other ideas.“She was like, ‘Don’t give it away, don’t give it away. Just be nice. Just be friendly,’” van Huet recalled. “‘That’s scary enough.’”Sosie Bacon stars as a therapist with her own issues in “Smile.”Paramount PicturesSosie Bacon, ‘Smile’Sosie Bacon hoped to do a horror movie, but not just any horror movie.“I wanted to do a good one and the right one,” she said in a video call from her home base of Los Angeles.She found it in “Smile,” Parker Finn’s exploration of childhood trauma in a scary-clown wrapping.Bacon is polished and hyper-confident as Dr. Rose Cotter, a therapist in a psychiatric hospital who numbs debilitating inner pain with work, the better to atone for the wrongdoings of her past.Then a patient starts screaming about a figure she can’t unsee before breaking into a diabolical grin and slicing into her own face. And Rose’s mask starts to crumble.“I was drawn to the psychological aspect of it massively because human beings and their psyches and therapy stuff, I just gobble it up,” said Bacon, 30. “It was important to me that there be this thing boiling under the surface.”And sometimes on it. That tic where Rose devours her cuticles with increasing intensity?“I also pick my fingers and they bleed, like, a lot so it wasn’t that difficult for me to go there,” she said.Bacon lived with her parents, Kevin Bacon and Kyra Sedgwick, when she shot “Smile” on the East Coast, and a few of Rose’s nightmares followed her off the set.“My dad has been in a gajillion horror movies, but it wasn’t until after the movie that he was like, ‘Oh yeah, it’s the worst. The worst thing to do is to have to be scared in different ways,’” she said. “I was like, ‘Why didn’t you tell me?’ And he was like, ‘I just didn’t want to ruin it.’”Sosie Bacon credits her stint last year as a recovering addict opposite Kate Winslet in HBO’s “Mare of Easttown” for the offer of Rose, her first lead. “I was able to make something of it and it had a lot of levels,” she said. “I think that showed people that I could really do it.”Now she’s aiming for something lighter, like a buddy comedy maybe. But the next time she ventures into darkness, she’ll prep with calming affirmations — and a reminder.“What I would say to someone taking on a horror movie is, ‘It’s not all fun and games.’”Anna Diop plays a Senegalese domestic worker dealing with a Manhattan family in “Nanny.”Amazon StudiosAnna Diop, ‘Nanny’“That was the easiest ‘yes’ I’ve ever come across,” Anna Diop said of taking on Aisha, a Senegalese domestic worker for an entitled Manhattan family, in “Nanny.” “I’ve known her my whole life.”Aisha is laser-focused on saving money to bring her young son to New York, despite the cost to herself. Similarly, Diop’s mother, a Senegalese immigrant who worked as a babysitter and nanny, brought her own family to the United States when Diop was 5. (The Sierra Leonean mother of the film’s director, Nikyatu Jusu, did domestic work as well.)“There are so many parallels to my personal life that my mother’s story is indistinguishable in a lot of ways from Aisha’s,” Diop, 34, said in a video call.Indistinguishable, perhaps, save for the inexplicable cracks that soon leave Aisha awash in a wave of madness.Diop, who is in Toronto to shoot Season 4 of HBO Max’s “Titans” as Kory Anders, a.k.a. the superhero Starfire, prepped for “Nanny” by color-coding every scene on giant corkboards so that she could track the ascension of the horror seeping in.“But outside of that, I approached it just as a human story,” she said, noting that she tried to keep Aisha grounded by working from a place of logic: Is her mind playing tricks on her or are these things really happening?“It’s a woman who is a mother who loves her child and who’s determined to do this one specific thing,” she added. “And the internal and external obstacles she faces in trying to do that is all my focus really needed to be about.”Still, the day the movie wrapped, Diop returned to her apartment and sobbed, a release she hadn’t allowed herself while filming.“I felt Aisha, throughout the story — and so many women immigrants can relate to this — was just holding it together because you need to get done what you need to get done, whatever other horror or trials are happening to you,” she said. “You just power through. And that was me during it.” More