‘The Book of Henry’ is a work of unreal genius

Jaeden Lieberher stars as Henry in “The Book of Henry.”Alison Cohen Rosa/Focus Features

“The Book of Henry” would be best categorized as a Magic Child movie — one of those sentimental melodramas that hinges on a brilliant kid (it’s usually a boy) who’s too sensitive for this world and who teaches all us shabby grown-ups life lessons before moving on. “Pay It Forward” (2000) is the epitome of the genre and proof that the more a Magic Child movie wants to tug on your heartstrings, the crazier it gets.

“The Book of Henry” tugs on your heartstrings like a cable technician yanking a stubborn wire through a wall. Accordingly, it is completely insane. The plot proceeds from the charming to the manipulative to the shameless to the demented in gentle steps that may lull some audiences the way a frog can be boiled to death by degrees. Others may watch this movie through their fingers, suspended in the delight that can attend a truly wrongheaded movie.

Henry (Jaeden Lieberher) is the Magic Child, an 11-year-old genius who lives with his single mom, Susan (Naomi Watts), and little brother Peter (Jacob Tremblay, the kid from “Room”) in upstate New York. Mom’s a diner waitress and an overgrown child; Henry manages the family finances by day trading, at which he is a pint-size Michael Bloomberg. The family lives in a ramshackle mansion that has been scrupulously art-directed to appear casual and creative.

“The Book of Henry” begins to edge toward the asylum when Henry discovers that Christina (Maddie Ziegler), a classmate who lives next door, may be being sexually abused by her stepfather (Dean Norris), who’s the town police chief. Unable to help the girl through official channels, Henry starts concocting a plan.

That’s when something terrible happens that I can’t spoil. Suffice to say that at this point “The Book of Henry” gathers itself in, pauses, and takes a long, considered swan dive into an empty pool.

The mission of murderous mercy becomes Susan’s, but, thankfully, she has Henry to guide her via a tape recording that lays out everything she needs to do, including how to buy a rifle, bullets, and a high-powered spotting scope from a shifty local gun shop. Susan talks back to the tape recording and Henry seems to “answer” her — that’s how smart this kid is! The movie dances along the edge of incredulity and bad taste before pulling back from the abyss in a way that feels even more mawkish and calculated. It’s the kind of movie where a school administrator (Tonya Pinkins) finally gets incontrovertible proof of Christina’s molestation by watching her dance.

The actors are good, especially the younger ones. Lieberher was the Magic Child in the much better “Midnight Special,” and he has a face somewhere between an old soul and an old shoe. As he did in “Room,” Tremblay conveys pluck and vulnerability with the naturalness of an actual kid. Watts beats upstream against the story’s implausibilities, but poor Sarah Silverman is stuck in the underwritten role of Mom’s Floozy Pal and Lee Pace grins manfully through his scenes as the handsome, caring neurosurgeon who the movie keeps pulling out of the wings hoping that Watts’s character will notice him.

You can blame a screenplay, by the best-selling crime novelist Gregg Hurwitz, that leans much too heavily on coincidence and contrivances, or you can blame the direction by Colin Trevorrow that lacks the fluky charm of his indie breakthrough “Safety Not Guaranteed” (2012) while embracing the plastic commercialism of his “Jurassic World” (2015).

Me, I blame the Magic Child. If he’s so smart, what’s he doing in a movie like this?

★ ½
THE BOOK OF HENRY

Directed by Colin Trevorrow. Written by Gregg Hurwitz. Starring Naomi Watts, Jaeden Lieberher, Jacob Tremblay. At Boston Common, West Newton, suburbs. 105 minutes. PG-13 (thematic elements, brief strong language).