Millie Bobby Brown on becoming a Victorian 'wild child' in Enola Holmes

Elementary this isn't, dear Watson: Millie Bobby Brown is taking sleuthing up to the high school level. The Stranger Things star puts a teenage twist on the tales of English literature's most famous detective as the title character in Enola Holmes (out Sept. 23), Netflix's film adaptation of Nancy Springer's YA series following the capers of Sherlock's spirited little sister (an invention of Springer's outside Sir Arthur Conan Doyle's canon), who shares the family talent for the art of deduction.

While her big brothers Sherlock (Henry Cavill) and Mycroft (Sam Claflin) have famed adventures in London, Enola enjoys an idyllic — if unconventional — upbringing in the countryside, where her free-thinking mother, Eudoria (Helena Bonham Carter), schools her in all disciplines except how to become a proper Victorian lady. When Eudoria mysteriously disappears and Mycroft insists on sending his untamed younger sister to finishing school, Enola runs away to find her mother — and her own future.

"That's when we really begin the coming-of-age story," says Brown, starring at last in a Netflix offering that allows her to speak in her native English accent. "Who is she, who is Enola Holmes, what does she stand for, what does she believe in? She was so confident, and yet can be so innocent and really not knowing of her future, which is like every teenager at this time in their life."

She lacks street smarts, but Enola finds her way in the big city by putting her mother's unorthodox lessons — including in the martial arts — to good use. "I 100 percent wanted to do all my stunts," says Brown, who had never done action on this scale before. "I don't want to make anything easy for myself!"

To prepare for fight scenes in alleyways and a London teahouse, Brown trained for nearly two months, both in and out of her cumbersome period costume. "I [had to] prepare my body to breathe and to move in the corset," she says. "It's hard navigating the choreography that you've learnt so well in your trainers and your leggings and then switching up and putting an underskirt on, a skirt over that, a corset, then you have your petticoat, then you have your long socks, then you have your heels…"

Brown's sister first brought Springer's novels to her attention, and "the story grabbed me and took me on an adventure the moment I opened the book." Inspired to see the project all the way through, the actress also picked up her first producing credit on the Harry Bradbeer-directed film. "I knew I wanted to do this. I knew I wanted to creatively take part," she says. "I feel like this is my baby."

Carrying a whole feature in the title role marks another first for the 16-year-old star. "On Stranger Things, with like 20 to 30 cast members, everyone gets their limelight," says Brown, who filmed Enola last summer after wrapping her third season of playing Eleven. "So walking onto the set and feeling genuinely empowered and feeling like I'd been given this platform was such an amazing opportunity, especially as a young girl." It's the kind of chance that would never be afforded to her 19th-century counterpart, brilliant though she is, which the film addresses when Enola leaves the intellectual utopia of her mother's household for the huge, unforgiving city. "We bring a certain sense of positivity and humor to it, but at the end of the day, [the film] is centered around equality," she says.

That message will likely resonate with Brown's young, rabid Stranger fan base, though they have over a century on the Victorian teen. "What they call [Enola] in the film is a 'wild child,' but really, she's just fighting for her rights," Brown continues. "The film is based upon these pretty traditional men — and these wild women."

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