Millie Bobby Brown is the title character, Enola Holmes. Many people know Brown (including me, although I didn't make the connection until after I'd watched the movie) as "Eleven" from "Stranger Things." Brown is also, I was interested to see, a producer. And given that she really is the age she's presented as being in the movie (16), that's a pretty lofty position. ("Executive producers" are figureheads, money providers, almost powerless. The real power rests with the plain "producers.") She's got a future.
Brown is both charming and very good in the lead, although I had some objections to her talking to the camera. That's fine with Deadpool (it's modern, and it's a comedy), less fine in a period piece. Enola is the younger sister of Sherlock and Mycroft - born of the book series "The Enola Holmes Mysteries" by Nancy Springer. As a fan of the Sherlock Holmes cannon (I've watched hundreds of hours of TV and movies, but ironically have never read any of the stories), I'm not entirely happy when the cannon is bent. And it certainly is here. I didn't mind the addition of Enola, I was a little shaky on the addition of her mother Eudoria (Helena Bonham Carter) ... although I suppose a 16 year old daughter implies the existence and involvement of a mother. What offended me most was their portrayal of Mycroft (Sam Clafin). He's not stupid, but he's nowhere near as bright as Sherlock. The problem is - he's a well established character, and in cannon he's easily Sherlock's intellectual equal. On the plus side, Henry Cavill (in a relatively small role) is perhaps the most charming Sherlock we've seen in the last couple decades. Although even with beautiful tailoring, you could still occasionally see his currently massive physique (he's been doing a lot of action: "Witcher," DC movies as Superman, like that). Which seems improbable for Sherlock. This last isn't really a complaint, it just amused me.
Another couple minor gripes: who knew that the London of 1900 was so diverse! According to this movie, an Indian police inspector (Lestrade, another cannon character modified) is normal, as is an African store owner. Neither of those things would have been possible in the time period. Likewise, the movie is all about what women can do, and women's rights: that's closer to reality, as women's suffrage was being debated at the time. Nevertheless the things that Eudoria, Enola, and Edith (the female African store owner) did in the movie would have been considered too outrageous to be accepted in society at the time. But of course my objections are overruled by the inclusive intent of the movie. The result is enjoyable ... I guess I just can't let these improbabilities pass without pointing out that wishing that's how London was in 1900 doesn't make it so.