If someone had told Outlander fans in Season 4 that the wayward, rebellious Brianna MacKenzie would come to be the pillar of stability in the Fraser family, they probably would have laughed them out of the Highlands. But in the waning episodes of the Starz series’ eighth and final season, the brilliant mind, wife, and mother has proven those days are behind her –– and Sophie Skelton, who has played her since Season 4, couldn’t be happier.

“I do feel that playing Brianna at this point in her life has been my favorite of her eras,” Skelton tells TV Guide. “I’ve always had so much sympathy for her. She was growing up figuring out those teenage years, which is hard enough, while also grappling with her paternity and the death of her father, and feeling like that was her fault. She’s kind of been through it, but she’s somehow become everybody’s rock. I often felt like she came with the chaos, and now I feel she is almost just this really calm, grounding voice of reason in the middle of all of the mayhem.”

That’s never been more evident than in the eighth episode of Season 8, titled “In the Forest,” which finds Brianna coming to the rescue on multiple fronts. When her half brother William Ransom (Charles Vandervaart) comes calling on the Ridge, he can’t bring himself to admit that he wants to see his father, Jamie (Sam Heughan), whom he largely resents but whom he can’t deny after he inadvertently learned that the man who raised him, Lord John Grey (David Berry), was gay. Poor William is the last to learn just about everything.

Instead, he says he’s there to see Brianna, whom he only met for the first time a few months prior in Savannah. He wants to confide in her that his new love interest, Amaranthus Cowden (Carla Woodcock), the fictitious widow of his cousin, has broken his heart. He’s hurt, angry, and acting out like a child, which is something Brianna once knew a little something about.

“It was very interesting to be able to be Brianna mentoring William, helping him to not make the same mistakes that she made,” Skelton says. “It was quite cool as an older Brianna, watching William essentially be young Brianna. It was like when people talk about hugging your younger self and forgiving your younger self. To be able to do that objectively with a sibling was a fascinating way to look at that.”

But perhaps her most consequential contribution in Episode 8 required a few things only Brianna can offer. The premonition of Jamie’s death at the Battle of King Mountain, courtesy of the history book written by Brianna’s other father Frank (Tobias Menzies), still looms over the family, but Brianna cooks up an idea to give Jamie an advantage on the frontlines. She and Roger (Richard Rankin) already successfully procured arms for the men of the Ridge for when the battle arrives, but they are rickety and rudimentary. However, Brianna’s engineering training from her life in the 20th century allows her to replicate –– or rather in 1780, invent for the first time –– the Hall rifle, a gun that can be loaded and fired more quickly than a standard gunpowder-dependent musket.

Through montage, the passing time of, which is marked by Brianna’s growing pregnant belly, shows her pouring metal and cobbling together her new invention, before showing it off to Jamie and company. Challenging her Da to a shoot off, Brianna breezes through the loading of her gun, and beats Jamie to the shot, yet again proving her usefulness in a time that otherwise doesn’t tolerate such progressive achievements from women.

To prepare for the scene, Skelton worked with the production’s armorer Scott Rogers to not only understand how it was made but also get comfortable with the Hall rifle Brianna has just handcrafted from nothing but a faint memory from 200 years in the future. Skelton relished the chance to build that familiarity so it was authentic when Brianna shows up her father. “I wanted to make sure that when I had that rifle bit with Sam, I absolutely did whoop his ass for real,” she says with a laugh.

While Brianna smirks a bit in the moment, her accomplishment is less about showmanship and more about contributing to the cause and giving her father more than a fighting chance at Kings Mountain.

“It was sort of just quietly, calmly executed,” Skelton says. “She just went away and got it done in a less loud version than maybe old Brianna would have. What was so great is that one of her biggest struggles throughout all of the seasons and all of her time-traveling periods has been that she’s not been able to authentically be her MIT-trained, engineer, intelligent, brain-forward self. It was just nice for Brianna to flex those muscles.”

The other revelation in the episode is that Frank’s foreboding book, which Jamie and Claire (Caitriona Balfe) have spent all season worrying was his way of punishing their love from the grave, wasn’t meant for them at all. Commending his daughter’s sharpshooter eye, Jamie learns her nickname is Deadeye, the person to whom Frank dedicated the book. In that moment, the Frasers realize he wrote the book so Brianna would know how and exactly when Jamie’s life would need saving –– if only she had read it.

“Maybe I’m just more nosy than Brianna, but I find it so interesting that she didn’t read the book,” Skelton says. “I know why she didn’t, because it’s hard and it’s probably the last piece of Frank that she wants to savor, like she did with Jamie and Claire’s letters. But come on, Brianna. Nosy up, babe! Open the book!”

Skelton doesn’t consider this news to be a twist, given she never doubted Frank always wanted to give Brianna the tools she needed to survive in her time and her real father’s. But that doesn’t mean Outlander isn’t in the business of twists in its final episodes. Last week’s shocking death of Fergus Fraser (César Domboy) in a deliberate fire at his print shop has left Fraser’s Ridge and fans in mourning. With only two episodes left, Skelton warns that those watching at home shouldn’t expect this week’s relatively calm and genuinely heartwarming display of quality time on the Ridge to be indicative of the rest of the series.

“It’s Outlander, right?” she says, trying to find the non-spoilery words. “You should always be bracing for something. We kind of build you up, get you really happy, get all the family together, put a smile on your face, and then we just tear your heart apart. Given that it’s the final two episodes of the entire series, I’d probably have a friend nearby and a box of tissues out. And maybe a dram (of something strong).”

Outlander airs Fridays on Starz, streaming on Starz.com.