Louisa Jacobson is opening up about her first reaction to Marian Brook’s Season 4 storyline on The Gilded Age, admitting she was “very frustrated” when she first learned what would happen to her character.

Jacobson, 35, has played Marian since the HBO period drama premiered in 2022. As she read the first episodes of the new season, she said she was “feeling a lot at once” about the direction Marian’s story was taking.

Season 4 premiered on Nov. 1 and finds Marian “forges a new path for herself,” according to HBO’s synopsis. Jacobson was especially excited to see a different side of Marian as she enjoyed more freedom and spent time downtown with Oscar and Enid Van Rijn.

“I think when I first got the first couple of episodes, I was feeling a lot at once. I was so overjoyed to see her have this downtown moment, and I was just getting so excited with all the ways that could … how I could do it,” Jacobson tells.

She was also happy to see Marian finally relax and enjoy herself.

“And just the release of finally feeling Marian’s release, and Marian’s joy, and her letting go and letting her hair down, literally,” she says.

Jacobson said it was particularly exciting to see Marian with her “shoulders out” and “corset out.”

But her excitement quickly changed when she read what happened the following day.

“To read what happens the next day” was “very tragic,” Jacobson says.

“It made me very frustrated at first, but then I really welcomed the challenge of conveying the stakes,” she explains. “It was almost like I was honored to be responsible for placing us in the 19th century when Victorian ideals of morality and purity were very, very strong and strict, specifically with women.”

In the Season 4 premiere, Marian reunites with her former love Larry Russell, played by Harry Richardson, while she is at a downtown club. The two share a dance before Larry offers her a ride home in his carriage.

A storm forces them to stop at a hotel. Although they initially take separate rooms, Larry later goes to Marian’s room, and the former couple spends the night together.

The next morning, Marian wakes up in a panic and quickly leaves.

Later, she tells Peggy, played by Denée Benton, that she “made a mistake” and that what happened “wasn’t appropriate.” Peggy tries to reassure her, telling Marian that she is being “too hard” on herself.

For Jacobson, Marian’s reaction makes sense because of the strict social rules surrounding women and sexuality during that period.

“Premarital sex was the biggest cardinal sin, and it could ruin your life, both externally if people found out and internally, because there’s internalized shame there from decades and decades of history,” she says.

Jacobson acknowledged that some viewers might struggle to understand why Marian reacts so strongly, especially because Larry is someone she cares about.

“I knew that maybe it would be difficult for an audience to understand because he’s so sweet, why is it such a big deal? But that’s just my job. I have to lean in, and I did and I’m proud of it,” she says.

She also believes the morning-after scene shows how isolated Marian suddenly feels as she realizes that the consequences could fall heavily on her.

“It also leaves her very alone at the morning after because she’s having this realization very fast in a panic state of mind, like the stakes are so high for me and he’s not going to suffer any of these consequences,” Jacobson explains.

The actress points out that women at the time had little education about sex or their own sexuality.

“You have to remember, women had no concept of sex, no education around their sexuality. Premarital sex, forget it,” she says.

She also finds Marian’s conflicting emotions interesting because what could have been one of the happiest nights of her life immediately becomes something she fears.

“And just to play with the complexity of something that probably was the greatest night of her life is something that is actually so bad is a very confusing thing to grapple with as a person,” Jacobson adds.

Richardson, 33, also discussed Larry’s perspective and admitted that his character is still learning just how serious the situation is for Marian.

“Larry is going through the education that the audience is going through” about the “depth of the stakes at hand for Marian,” Richardson tells PEOPLE.

He explains that Larry’s intentions were more serious than simply having a casual encounter with his former girlfriend.

“I think his intentions were a lot more than having a dalliance that day with an ex. It was like, he really wants to be with her,” he says.

However, Larry did not understand the consequences his actions could have for Marian.

“He didn’t realize that that was a big miscalculation on his part. And that just showed how ignorant he was and how much he didn’t understand yet about what her experience was at the time,” Richardson adds.

Marian’s story is just one part of the larger Season 4 drama. Bertha Russell, played by Carrie Coon, has “changed society at a cost,” according to HBO, leaving her family to deal with the consequences.

Agnes van Rhijn, played by Christine Baranski, is also looking for a chance to regain her position, while Peggy continues working toward acceptance from her future in-laws.

The cast also includes Morgan Spector, Cynthia Nixon, Jordan Donica, Taissa Farmiga, Blake Ritson, Ben Ahlers, Ashlie Atkinson, Dylan Baker, Kelley Curran, Jessica Frances Dukes and Amy Forsyth.

The Gilded Age airs Sundays at 9 p.m. ET on HBO and is available to stream on HBO Max.