Review: 'Baby Ruby' is an unsettling thriller about new motherhood, bolstered by French star Noémie Merlant's passionate performance.

The psychological thriller “Baby Ruby” does some fascinating things with a familiar idea: That one of the most terrifying things a woman can face is new motherhood.

Joséphine, played by French actor Noémie Merlant (“Portrait of a Lady on Fire”), has built a small business out of her personal brand as a social-media influencer and blogger — sharing her picture-perfect life with the world. She and her husband, Spencer (Kit Harington), an artisanal butcher, have built a beautiful home upstate, and are getting ready to greet their baby daughter, Ruby.

After Ruby’s birth — a rather blood-filled experience — Jo finds caring for her new baby a tougher battle than she thought. Jo is up at all hours, either trying to get Ruby to stop crying or strapping on the breast pumps to express milk for later. Sleep deprivation sets in, and Jo begins to think something’s horribly wrong with her baby.

Seeing the other moms in her town — in particular Shelly (Meredith Hagner) — all smiling and serene with their babies, just sets Jo spiraling even further. She starts to think she can’t trust her pediatrician (Reed Birney), her mother-in-law (Jayne Atkinson) or even Spencer.

Playwright Bess Wohl (whose play “Grand Horizons” was nominated for two Tonys in 2020) makes a sure-footed directing debut, squeezing Jo’s postpartum fears into the shape of a horror thriller. Her smartest move in “Baby Ruby,” though, was casting Merlant, who captures Jo’s journey from confident influencer to terrified new mom with convincing levels of panic and horror. 

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‘Baby Ruby’

★★★

Opening Friday, February 3, in theaters. Not rated, but probably R for bloody violence, some nudity and sexual content, and language. Running time: 92 minutes.