With On Chesil Beach, which will be in theaters next month, Saoirse Ronan sustains an unbroken streak of acting excellence that has encompassed The Grand Budapest Hotel, Brooklyn, and Lady Bird. The film is set in the narrowest sliver of historical time, the immediately pre-youthquake Britain of 1962, when, as Ian McEwan writes in the novella upon which the movie is based, “to be young was a social encumbrance . . . a faintly embarrassing condition for which marriage was the beginning of a cure.”

But the picture, directed by Dominic Cooke and co-starring Billy Howle, is tender toward its virginal newlywed protagonists rather than mocking and mean. “Satire creates distance. I wanted the reader, and now the viewer, to get right up close to them,” says McEwan, who handled the screenplay adaptation himself.

In bearing and appearance—”certainly beautiful, but in a sculpted, strong-boned way,” as the book has it—Ronan is uncannily right for the role of Florence Ponting, the violinist who takes the hand (but not willingly much else) of her groom, Edward Mayhew. “The physicality of Florence is so important, because there is so much that isn’t said,” Ronan explains. “And Ian writes with such love and understanding. I don’t think there are many films that have tackled this subject this way. Usually, it’s either a caricature, like American Pie, or overly sentimental.”

For McEwan, the admiration is mutual. This is his second movie with Ronan; at age 13, she received her first Oscar nomination for playing the troublemaking Briony Tallis in the film adaptation of his novel Atonement. “I can no longer remember these characters as I once envisioned them,” McEwan says. “Saoirse had already kidnapped Briony. And now I’ll forever see her stalking the beach as Florence.”