The actress says fans are 'really in for a ride' as the History drama approaches its season finale.
We haven't seen the last of Princess Isabella.
King Philip and Queen Joan's daughter has seemingly flown under the radar over the last few episodes of Knightfall, after orchestrating the death of her betrothed, Prince Luis, and almost doing the same to her accomplice, William De Nogaret. On this week's episode of the History drama, however, Isabella is back -- and perhaps darker than ever.
"Do not underestimate how far she has come in learning to be a ruler, and also the darker side to her. If we think we've seen that now, we're really in for a ride," Sabrina Bartlett tells ET. And like her character, the British actress has quite a range.
Bartlett grew up with dreams of becoming a ballerina. Just a few years later, her acting ambitions got her on the set of Doctor Who, Da Vinci's Demons and Game of Thrones before scoring her biggest -- and most complex -- role yet on Knightfall.
"This is the type of role you dream of of playing and portraying, not just a variation in a journey of emotions, but also challenging and finding truthfulness of her actions and her character," she gushes. "It's really satisfying to play. The stakes are massive for her, and she has a shift in who she trusts and where her interests lie, and has this sexual awakening with her relationship with the prince and [De Nogaret]. It really was a roller coaster."
One thing that helped Bartlett get into character as the cunning Isabella was reading a lot of Shakespeare's Macbeth. The other was Knightfall's production schedule.
"We read the episodes while we were shooting the series, so we didn't even know how dark she was going to become," she explains. "It was just really useful in terms of acting, to truly be experiencing each moment with no idea or preconceptions of what was to come next. I really was discovering her as we were shooting."
"I think there's something in her still being a child...She is quite rash with her decisions, and it is quite dark as well, but once you cross her, [you] will be very, very sorry," Bartlett continues, adding that Isabella's dark side was ignited by her purity test after sleeping with Prince Luis. "I think that's where the gates come down, and the darkness just eclipses her personality, and she has this need for revenge. She has this need to exact the pain and hurt and humiliation that she has felt, and I think that is absolutely the driving force of her actions."
Isabella's change was also signified by her evolving wardrobe, trading bright, romantic dresses for black and gray cloaks, courtesy of costume designer Diana Cilliers.
"In the beginning, it's very symbolic of her being a young woman, she's getting ready to marry, she's very much in love, so that's reflected in these very soft, very pretty light fabrics," Bartlett describes. "And then once the death of Luis happens, she's in mourning, which is [reflected in] a very stern and very formal attire. She's got almost like a wimple around her face, and I feel like it's her mask. It helps her to provide this disguise so that the court and her parents will believe that her grief is real."
Viewers will see Isabella's wardrobe change again on Wednesday's episode, marking a new chapter in her life as tensions rise between Philip and Joan and the Knights Templar's search for the Holy Grail. As for whether Isabella and De Nogaret will ever fight on the same team again, Bartlett admits that might be a question answered in season two.
"If history's anything to go by, Isabella famously marries Edward II and became the queen of England, and I think De Nogaret would be absolutely behind that decision. It's his ambition to see her succeed as a ruler, and Isabella has lived and breathed in preparation for becoming a powerful queen," the actress notes. "I can only imagine they would achieve that together if the series should go again."
Knightfall is still awaiting season two renewal, but Bartlett is more than ready to step back into character.
"The roller coaster of tackling Isabella for me was such a learning curve, and also such a joy to experience alongside such seasoned actors," she says. "Learning from Ed Stoppard and Olivia Ross and Julian Ovenden, they really took me under their wing...I really did feel that we were a family."
Knightfall airs Wednesdays at 9 p.m. ET/PT on History.