"Teachers, they have it easy!" exclaims a father early on in Serge Bozon's dutifully unclassifiable comic-horror schoolhouse lit-adaptation curio Mrs. Hyde. That father says this in a swimming pool just moments after he has accidentally splashed Mrs. Gequil, the film's lead, played by Isabelle Huppert. Gequil has spent the day suffering the put-downs, disinterest and persistent jabbering rudeness of her physics students at a local high school. That dialogue bodes poorly for the film to follow: The irony is as broad and bald as a hippo's belly, the kind of comic indignity a studio crowd-pleaser might foist on Ben Stiller.
At its worst, Bozon's film strains to show us what we already know. Teaching teenagers ain't easy, of course, and Isabelle Huppert is luminous. Bozon (Tip Top) emphasizes that via wholly unnecessary special effects, buttering his star up in a superhero's sheath of golden light. The story, loosely adapted from Robert Louis Stevenson's novel of the monster within, finds Gequil transformed into a murderous electric sylph after lightning strikes the high school's laboratory. Enter Mrs. Hyde, who stalks the Paris suburbs at night and kills the occasional teenager while wreathed in light that obscures the very visage audiences will have paid to see.
The story's key twist is that Hyde's rapaciousness inspires Gequil to new confidence in the classroom. The movie comes to life most often in its back half, when the tone sours, the killing loses all veneer of comedy or karmic justice and Gequil finds herself at last recognized for her excellence as a teacher and haunted by her other half.