“Greta,” a fun, but ultimately watered-down play on a classic, campy cat-and-mouse movie, isn’t anything we haven’t seen before, but strong performances by Chloë Grace Moretz and Isabelle Huppert will a blatantly mediocre screenplay to the finish line.

The premise here is really simple: Moretz plays Frances McCullen, a young Bostonian starting her new life with her best friend, Erica (Maika Monroe), in a plush New York apartment. After a long night of serving expensive dishes to some high-class clientele at the restaurant she works at, Frances takes the subway home and notices a purse left unattended. She takes it home and sees it belongs to a woman named Greta and decides to do the right thing — or as Erica describes it, the very non-New York thing — and return it to her. When she takes the purse back, she sees Greta is a sweet old woman, and the two quickly form a bond.

But not everything is as it seems. Specifically, Greta is a bit of a nutcase, stalking Frances when she decides to sever ties after realizing Greta left the bag on the train on purpose to try to reel in some kind soul to keep her company.

“Greta” is carried entirely by some inspired performances from Moretz and Isabelle Huppert as the eponymous psychopath. Moretz is on a bit of a hot streak coming off the heels of last year’s Sundance Grand Jury Prize winner, “The Miseducation of Cameron Post,” and her powerful one scene performance in Luca Guadagnino’s “Suspiria” remake, some of the most dedicated acting I saw last year. Here, Moretz is pitch perfect as the girl who’s too nice for her own good, to the point where her own kindness gets her in more trouble than it gets her out of. Moretz plays a girl from Boston in “Greta,” but it’s hard to imagine she didn’t draw on her Southern roots for the performance.

Moretz’s performance was lifted even higher being next to such an accomplished actress as Huppert. Most American audience members probably have no clue who she is, but the French performer is a legend in her own right, appearing in over 130 films since 1970, most notably in Michael Haneke’s 2012 Best Picture-nominee “Amour” and in her Cannes Best Actress award-winning performance in 2001’s “The Piano Teacher.”

Huppert steals the show whenever she’s on screen. At times, she’s a sweet old woman who no longer has a connection to her daughter and is just looking for human interaction wherever she can find it. But when Huppert wants to turn up the creep factor, she has it in spades. She’s chilling when she needs to be with a constant underpinning of sorrow and loneliness, and her performance blended with Moretz’s elevate “Greta” exponentially.

Unfortunately, “Greta” is a film that badly needed elevating thanks to a dreadfully drab, dull screenplay from director Neil Jordan and co-writer Ray Wright. This movie is just begging on its knees to let its hair down and get as weird as possible, but the film, maybe due to its studio’s wide release, just never lets itself out of the box. (That last sentence will be a really funny pun after you’ve seen the film. Trust me.)

This was a film I was really looking forward to, mainly because of the two leading performers, and they delivered as well as they could, but the movie is incessantly dragged down by the filmmakers’ seeming unwillingness to take a big risk. In a movie that could’ve been so delightfully bizarre, unfortunately “Greta” is dragged down as an experience by being way too cookie-cutter.

(That’s another pun.)

GRADE: C+

Cameron Hoover is a film critic. Contact him at [email protected].