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Casting Brianna was no walk in the park — or stroll through the Highlands, rather — for the producers of

As if finding the perfect actors to play Jamie and Claire wasn’t hard enough, executive producer Ronald D. Moore said it was “difficult” to track down a young woman who could pass for their daughter. Ditto for Roger (Richard Rankin), the man who would eventually become Brianna’s romantic interest in the ongoing saga.

“They’re very tricky roles to cast, especially when you’re casting the adult child of two of our leads,” Moore tells EW exclusively. “You want to see both characters in her immediately, which is a big challenge, just in terms of who that actress is going be. She also has to play, literally, the daughter of Claire in the 13th episode. And she has to have a certain chemistry with Roger. Even though she’s in that episode very strongly, she’s not as strongly in the next season. The role of Roger and Brianna grows over the course of the books. But at first, you’re just seeing the two of them for briefer periods of time. So yeah, all these things add up to a very complex process, trying to find the woman who would fit all these parameters.”

Enter Sophie Skelton, a 22-year-old newcomer from the U.K., who admits there was plenty of hand-wringing over her inaugural appearance. Her first scene had to be reshot because her newly-dyed hair was too wavy and inappropriate for the time period.

“We had trials,” she tells EW. “Obviously, trying to get the red right and sorting out styles. Our first day was actually a 16½ hour shoot. The hair wasn’t quite right. So, we ended up doing it again…. Brianna is supposed to have the same kind of curly red hair as Jamie, but it’s the ’60s so it would be more straight with the fashion. So yeah, we ended up changing it.”

which will wrap up its second season on July 9 — pick up the latest issue of

on newsstands. And don’t forget to tune in to Monday’s edition of

! on EW Radio. Sam Heughan will be our guest! The hour-long show airs Mondays at 2 p.m. ET on Sirius XM 105.

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