Novels are more accommodating of psychological inscrutability than plays. For this reason, preparing Muriel Spark’s brilliant but sparse novella, “The Prime of Miss Jean Brodie,” for the stage was no easy task for actress Cynthia Nixon, who plays Miss Brodie in the current revival at the New Group, and her director, Scott Elliott. The play, which was adapted by Jay Presson Allen and first produced in 1968, arranges Miss Brodie’s memorable speeches into a series of scenes that replace the temporal back-and-forth of the novel. But it is up to the individual actress and director to find the character’s flesh and blood.

Ms. Nixon said she found a clue to the character — a charismatic, unorthodox girls’ school teacher in 1930s Edinburgh ––on a brief trip to Scotland before rehearsals began.

“I found this incredible book, kind of a history of World War I through poetry, that told you about the progress of the war, and the early enthusiasm for it.” (The book is “Minds at War: The Poetry and Experience of World War I,” edited by David Roberts.) In terms of understanding Miss Brodie’s perspective, Ms. Nixon said, she found the descriptions of the pro-war sentiments very helpful. Miss Brodie glamorizes war, telling her students romantic stories about a lover who died in World War I. She is ultimately fired when a student alerts the headmistress to her championing of fascism.

Ms. Nixon said the book helped her understand “how closely linked the idea of service was to the idea of being a student and being on a team, and that enshrining of self-sacrifice.” She came to believe Miss Brodie was shaped by these wartime ideals.

That Ms. Nixon needed to search outside the novel and play for clues to the heroine’s motivations is telling of Spark’s economical style. The literary critic James Wood has described Spark’s novels as “fiercely composed and devoutly starved,” meaning that she presents the reader with a skeleton of facts, with no padding of psychological analysis. Miss Brodie, ostensibly the book’s central character, is also in some ways its least developed.

Miss Brodie does, as Ms. Nixon observed, make sacrifices: She gives up the man she loves, the married art teacher, Teddy Lloyd, and instead carries on an affair with the music teacher, Gordon Lowther. And she famously tells her girls she would sacrifice herself for them: “‘If I were to receive a proposal of marriage tomorrow from the Lord Lyon-King of Arms, I would decline it,'” she says.

But she also uses people, like Mr. Lowther and her students. “There’s a calculatedness to Ms. Brodie, and a greediness,” Mr. Elliott acknowledged. “She creates her world the way she wants it.”

To Ms. Nixon, this is a physical reaction to the strict philosophy of sacrifice Miss Brodie has embraced. “I think if you subject yourself to that kind of self-sacrifice, your body is not going to take it; it’s going to come dribbling out around the edges,” Ms. Nixon said. “Her rhetoric is very much about self-sacrifice, but then there is a lot of assertiveness and grabbing and demanding. Her whole body is having a natural reaction to it.”

At the same time, Ms. Nixon said, in a way Miss Brodie actually prefers the deferment of her desires to their satisfaction. If Teddy Lloyd were “available, and she actually married him and got fat and happy, it would diminish if not kill her motor,” Ms. Nixon said. “She knows that.”

Mr. Elliott and Ms. Nixon first planned this collaboration several years ago, when they worked together on “The Women.” Although they clearly work well together, like any actor and director, they occasionally have to reconcile differing views of the character. It seemed, to a reporter who spoke to both, that Mr. Elliott is more interested in Miss Brodie’s seductiveness and power, while Ms. Nixon focuses on her vulnerability and longing.

Ms. Nixon described, for instance, how they disagreed in their interpretations of the final scene between Miss Brodie and her student Sandy, who has just betrayed her to the headmistress.

“He really felt that, when Brodie walks through the door and sees Sandy, she’s convinced that Sandy is the person who has turned her in,” Ms. Nixon said. “And I was like, ‘I don’t know about that.’ But he felt it was important, because that’s such an empress type of thing [to do]: When you’re the queen, you’re always waiting for the person to try to assassinate you, to stab you in the back, to poison you. That kind of ever-vigilant paranoia comes with the feeling that you are very, very important.”

Mr. Elliott also pushed Ms. Nixon in the aspects of the character that are most different from her own personality — like Miss Brodie’s enjoyment of danger. “She’s one of those people who has that gene that makes them walk a fine line between what they should do, and what they know they probably shouldn’t do,” Mr. Elliot said.

Personally, Ms. Nixon may have more in common with the character of Sandy than with Miss Brodie. In creating Miss Brodie, she drew on two experiences, the first being her memory of being one of a group of chosen favorites, like Miss Brodie’s girls. “I thought about one elementary school teacher,” Ms. Nixon recalled. “He wasn’t nearly this focused, but he did have this group of six of us who would always hang out with him after school. We were his special girls. He would buy sodas, and we would all sit around and talk everyday. It was understood that he thought that we were the smartest.”

But Ms. Nixon also remembered keeping her distance from teachers who seemed to be manipulative. In high school, she said, she disapproved of teachers who pushed their own political views, as Miss Brodie tries to induct her students into admiring Mussolini and Hitler. “I was never really in that crowd,” Ms. Nixon said of these teachers and their acolytes, “because I felt it was done a little bit in a blackmail-y way. It was set up as a moral issue. There was right and there was wrong, and if you were with them, you were, of course, in the right. And if not –– well, it was kind of sad that you weren’t more dedicated. I never fell in with them,” she added, “but they were there.”

Opens October 9 (410 W. 42nd St., between Ninth and Tenth avenues, 212-279-4200).