Henry Cavill will play the famous fictional detective Sherlock Holmes in a movie that's not about Sherlock Holmes. Instead, Enola Holmes will focus on Sherlock and Mycroft's much younger sister, the title character. The teenage sleuth sibling may be an original creation of novel series author Nancy Springer, but her adventures pull from the established canon of Sir Arthur Conan Doyle's beloved stories. Soon, fans of the books will be able to see Enola come to life on the big screen as Millie Bobby Brown is set to star in the title role.

As THR reports, Cavill will come aboard director Harry Bradbeer's adaptation as Sherlock; Helena Bonham Carter also stars as the Holmes siblings' mother. And those signs point to the first of Springer's books, "The Case of the Missing Marquess", as the inspiration for the movie. Screenwriter Jack Thorne (Wonder, His Dark Materials) turned in the script, but plot details are few and far between. Let's see what we can figure out so far.

Since Springer's six-book series started with the disappearance of Enola's mother on her fourteenth birthday, it's probably a safe bet that the possible film franchise will start there, too. The story sees Enola's older brothers dismissing her concern over their mother's vanishing act and opting to send her off to a boarding school in the interim. But Springer's hero is a progressive character, so Enola takes matters into her own hands and attempts to solve the mystery herself. That takes her into the path of her older brothers and a case they happen to be working on, and Enola lands square in the middle of it.

It's more of a "Anything you can do, I can do better" kind of tale than it is a story of collaboration and mentorship, so I don't know how big of a part Cavill and whoever is cast to play Mycroft will have. But considering that Springer has five more novels after that, this could be a solid younger-skewing franchise for Legendary if it connects with audiences.