Katherine Waterston, left, and Vanessa Kirby in “The World to Come.” Vlad Cioplea/Bleecker Street

Abigail, the protagonist of “The World to Come,” keeps a diary, which, along with thoughts laid down in her letters, provides the narration for this film, set in 1856 in rural upstate New York, and centering on the unhappily married wife of a dour farmer named Dyer (Casey Affleck). When Abigail (Katherine Waterston) mentions that she’d like Dyer to pick up an atlas for her when he next rides into town – she’s saved up 90 cents of her own money – he suggests that it might be better spent on buying him a gift.

“What better gift could I give him than a wife who is no longer a dullard?” she thinks to herself (while saying the words to no one but us).

Maybe that’s the problem with their marriage. The interiority is stifling, and we feel as much claustrophobia, of the emotional as well as the physical kind, as Abigail surely must.

Based on the title short story from a 2017 collection by Jim Shepard, the film follows what happens when Abigail meets Tallie (Vanessa Kirby), a pretty neighbor who, with her husband, Finney (Christopher Abbott) – a match for Dyer in asperity – has started renting a neighboring farm. Shepard is the kind of writer who fills his historical stories with delicious period details: an enema of molasses, warm water and lard – with a drop of turpentine next to the nose – is a remedy for a cold. And that sensitivity to language and attention to detail carries over to Mona Fastvold’s film, which has been adapted for the screen by Shepard and Ron Hansen, who is also a novelist (“The Assassination of Jesse James by the Coward Robert Ford”).

“In earliest youth,” Abigail writes, “I was like a pot-bound root: all curled in upon itself.”

And, after Tallie and Abigail have established a rapport: “When (Tallie) arrives, my heart is like a leaf, borne over rapidly moving water.”

OK, so “rapport” is something of an understatement. “The World to Come” is a love story, between two women, in a world in which men hold all the power, and wives are treated almost like property. Initially, it is a story of pot-bound passion, all curled in upon itself – until, of course, it isn’t.

Christopher Abbott and Vanessa Kirby in “The World to Come.” Vlad Cioplea/Bleecker Street

With all this writing going on, right under the noses of two men who aren’t so thickheaded as to miss an affair between their wives, there are early warning signs that “World” isn’t going to end well. But Fastvold, a Brooklyn-based Norwegian actress and filmmaker making only her second effort behind the camera, never gins up the sentiment, the melodrama or even the sensuality. Like Abigail, she’s all about sublimation. Until very late in the film, we’re not even sure exactly what has been going on between Abigail and Tallie, when Fastvold shows it to us, suddenly and in flashback, as if flipping through the pages of a notebook she’s found.

This reticence, this coyness, has the opposite effect than what you might think. Instead of denaturing the ardor – the ecstasy, the rapture, the ultimate tragedy – of the story, Fastvold’s light hand only intensifies it. The filmmaker takes a page, beautifully, swooningly, from something Tallie tells Abigail, about how deep feelings can lie hidden in plain sight: “It’s been my experience that it is not always those who show the least who actually feel the least.”