If movies are to be believed, sleepaway camps provide the setting for one of two things: personal awakening in the form of new friendships or bloody murder by psychosexual slasher. Finally, there’s a film that combines both—Jane Schoenbrun’s “Teenage Sex and Death at Camp Miasma.” In the movie, Hannah Einbinder (of “Hacks” fame), playing a filmmaker who’s been assigned to reboot a classic horror franchise, and Gillian Anderson (of “The X-Files” fame), as the reclusive actress who played the franchise’s original “final girl,” talk about their feelings and hook up before Einbinder is chased across the camp by a spear-wielding killer named Little Death.The other day, Einbinder swung by Halloween Adventure, a year-round costume superstore in the East Village, and perused one of many walls of options: “70’s Blacklight Shirt,” “Metallic Foil Print Tiger Disco Shirt,” “Disco Shirt—Purple Circles,” all modelled by the same man on their packaging.“Talk about a beautiful subculture—the plastic-bagged-costume-model industry,” Einbinder mused. “In the waiting room of the casting office, everyone’s, like, ‘Fuck, Jerry’s here. You remember Jerry? From “Flower Power Disco Shirt”? He’s going to book it. I have no shot.’ ” Einbinder, who is thirty-one, wore a tailored gray suit and tinted glasses. For Halloween one year, she and the comedian Sandy Honig both dressed as Wayne, from the movie “Wayne’s World”—“because we both identify more with Wayne than Garth.” They’d made a pact that all their future costumes would be “strictly from the Mike Myers universe—so this coming year we will be fembots, and so on,” she said.She admired the knockoff “Austin Powers” costumes, such as “60’s Mr. Mojo,” then strolled to the killer-clown section (separate from clean-cut clowns), where she tried to recall Halloweens of her youth. “I have to do a little bit of work to access my childhood in general—give me one second,” she said, tapping fingers against her face and arms. She explained, “I’m just doing a little E.M.D.R. to launch myself back.” (E.M.D.R. being eye-movement desensitization and reprocessing, a psychotherapy trauma treatment.)“My parents were sober when I was growing up,” she said. “And, oftentimes, when people don’t do drugs or alcohol anymore, they have to have something fun—in many cases that’s sugar. So they would do drug-addict behavior around my Halloween candy. They’d be, like, ‘O.K., guys, you can have nine pieces tonight and then we’ll talk tomorrow about how much. . . . ’ And my candy would be gone in the morning.” Einbinder’s mother, Laraine Newman, was one of the original cast members of “Saturday Night Live”; Newman posed as a vampire for a 1978 issue of High Times, which described her as a “skinny spaced-out sex symbol.”In “Miasma,” Einbinder and Anderson have sex on a fireside carpet of candy wrappers, which were not added in post. “Yeah, that’s all practical—practical sex, practical candy, no extras there,” Einbinder said. It turned out that she and Schoenbrun are both “total sugar-heads.” Einbinder has a particular taste for sour. “I recently went to a 7-Eleven that had the new BUBS, which is a Swedish candy. They’re like diamonds,” she said, reverently. “They’re flavored tutti-frutti, which is not really in the American palette. It’s somewhere in a bubblegum sort of citrus-forward area.”She turned her attention to a “Pit Dweller” costume (one size fits most, up to six feet, two hundred pounds) that was basically a skin suit, with bulging ribs, long bloodied fingers, and a gaping fanged mouth for a face. It hung near a classic skeleton costume. “So, it’s actually exciting, because you can look to the influence,” Einbinder riffed. “ ‘Pit Dweller’ was only made possible by ‘Skeleton Adult Costume,’ which we can clearly see as a response to the First World War.”