Sydney Sweeney and Amanda Seyfried square off in Paul Feig’s “The Housemaid”, a movie that starts off as a fun campy throwback before nosediving in its final act by taking the cheapest and most predictable route available. It’s a shame because Feig has all the ingredients he needs, from a game cast to a genre formula that audiences tend to enjoy. But all of its entertaining buildup is wasted on a ridiculous and trite final act that narratively and thematically rehashes ideas we’ve seen several times before.

In fairness, “The Housemaid” is based on Freida McFadden’s 2022 novel of the same name and from all indications it sticks pretty close to the book’s central story. But if you’re unfamiliar with the novel and hoping for a movie with the slightest original punch, you might leave this adaptation disappointed. For me, seeing potential squandered for something this obvious is more frustrating than disappointing.

Sweeney plays a young woman named Millie Calloway who we first meet as she’s arriving at a lavish estate in Great Neck, New York. There she meets Nina Winchester (Seyfried), a wealthy wife and mother who has invited Millie to interview for a live-in housemaid position. It’s an important opportunity for Millie who isn’t quite who she claims to be. While she hides it from Nina, we learn Millie is fresh out of prison after serving ten years of a fifteen-year sentence for a crime which comes to light later. And she needs a steady job to meet the requirements of her parole.

Millie gets hired and wastes no time moving into a cramped A-frame attic space in the Winchester’s home. The converted bedroom isn’t much, but it beats sleeping out of her car. Millie is also introduced to Nina’s young daughter Cece (Indiana Elle) and her hunky husband Andrew (Brandon Sklenar). It looks like the ideal scenario for Millie. Cleaning, organizing, some light cooking, and helping with Cece in exchange for living in a nice house with a nice family for a nice salary.

But of course Millie’s scenario turns out to be far from ideal. It starts with Nina’s wild fits of rage. She then begins lashing out at Millie, blaming her for things she hasn’t done. Things get even more twisted when Nina begins framing Millie to make her look foolish. In normal circumstances, Millie would quit on the spot. But she desperately needs the job to stay out of prison. Thankfully she finds an ally in the endlessly charming Andrew who routinely steps in to reassure and reinforce Millie with his dreamy eyes and winning smile.

Without giving too much away, screenwriter Rebecca Sonnenshine wastes no time ratcheting up the drama before eventually turning the story on its head. Seyfried does unhinged well while Sweeney wins our sympathy and our suspicion. But neither performance hits every right note, mostly due the material. The script cunningly pushes both characters to their breaking point only to undo its own good work with a lame reveal that’s more interested in being relevant than original.

Sadly the predictable big twist lets all the air out of “The Housemaid”. Not only does it sour the good stuff that came before it, but it kills the film’s finish where things get wackier and bloodier. But even without the story’s eye-rolling “surprise”, the final 20 minutes are a wobbly mess. It’s an ending littered with arbitrary actions, an overly long explain-it-all flashback, and a final scene with ludicrous implications. But to be honest, by that point it didn’t really matter. The damage had already been done.