It is hardly believable that there’s yet another Sherlock Holmes ripoff/spinoff – the genre named by the late critic Gilbert Adair “Shlock Holmes”. But here is Sherlock’s little-known rebellious kid sister Enola, invented in 2006 by the YA author Nancy Springer. Jack Thorne has adapted the first volume in her award-winning series and the director is Harry Bradbeer.

Millie Bobby Brown (from TV’s Stranger Things) plays the imaginative, brilliant, quirky young Enola. She has grown up alone in the country with her enigmatic widowed mother, Eudoria (Helena Bonham Carter), who has homeschooled her in science, literature and martial arts – this is after Enola’s terribly grand older brothers, Sherlock (Henry Cavill) and Mycroft (Sam Claflin), have left home. But Eudoria herself disappears, leaving gnomic clues for Enola as to why, and then grumpy Mycroft insists on putting Enola in a stuffy boarding school run by Dickensian headmistress Miss Harrison (Fiona Shaw). So Enola has to escape, solve the mystery of her missing mum and also come to CGI Victorian London, thwarting a reactionary conspiracy to kidnap a handsome young aristocrat (Louis Partridge) who has a crush on Enola.

It all rattles along amiably enough. Enola Holmes is the kind of all-star production that might once have been made by the BBC and graced the front cover of the Christmas Radio Times. Brown has a nice, easygoing way with the material, cheekily outpacing her famous brother Sherlock here and there and often doing fourth-wall breaks to smirk at the audience, and I loved Miss Harrison’s steampunky motor car. But there should have been more specifically ingenious deducting and solving from Enola – codebreaking isn’t the same thing. So … is Moriarty’s super-evil kid sister on the way?

• Enola Holmes is on Netflix.