Natasha

Ms. Soo, known to friends as Pippa, had been acting since childhood in suburban Chicago. At 11 she had an agent and scored some work in commercials; she studied dance and improv and acted in high school productions, before landing a coveted spot at Juilliard, one of the nation’s leading performing arts schools.

The theater industry keeps an eye on Juilliard grads, and Ms. Soo was spotted quickly — she signed with a New York agent through the senior showcase, and in the days after graduating went to audition after audition. “Great Comet,” adapted from a section of “War and Peace,” was about her 10th casting call. “I had no idea what to expect,” she said. “I honestly thought, ‘O.K., this is like, a little bit strange, and I’ve never heard anything like this before.’”

Ms. Soo said her only goal was “to make a good impression.” And she did.

“She was dressed like Annie Hall, she played the ukulele, and it didn’t hurt that she had a voice like a nuclear weapon,” recalled Rachel Chavkin, the show’s director.

Ms. Soo was not the first person to play Natasha — that was Cristin Milioti (a Tony nominee for “Once”) in an early workshop — but she joined at the start of rehearsals for the first production, and played a key role in helping shape Natasha, a Russian countess spending time in Moscow while her fiancé is at war.

“Pippa and I worked really hard to make sure Natasha was as interesting as possible — to get out of the box a female ingénue often gets trapped in,” Ms. Chavkin said. “I needed someone who had the grace and the period-ness of the thing, but also had a violence within, and that is something Pippa was able to straddle.”

Ms. Soo had a similar goal for the character. “So often I felt like I was giving up a part of myself in order to play this ingénue — either dumbing myself down, or making myself more frightened or scared,” she said. “I finally saw an ingénue that I connected with, and I didn’t feel like I was giving up a part of myself, because the material asked for so much more.”