Their first meeting does not go well. Shirley Jackson (Elisabeth Moss) writes with force and intensity, but when Rose (Odessa Young) approaches her at the summer house party to introduce herself and compliment her work, the writer is brittle, bitter, and distant. She is, we discover, both depressive and agoraphobic; she hasn’t left the house in longer than anyone can remember, and most days, she can barely get out of her bed. 

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She can’t keep up the home she shares with her husband, Stanley Hyman (Michael Stuhlbarg), much less write anything new. “You can’t expect me to indulge this, can you?” he demands, and decides she can’t. Instead, he asks Rose and her husband Fred (Logan Lerman), who has come to assist Stanley at nearby Bennington College for the summer, to stay with them and lend a hand. Rose hears plenty of local gossip about Shirley. “She went sick in the head,” Rose is told. And at first, she has little reason to think otherwise; Shirley is combative and abusive and resents her new babysitter. “I like you, Rosie. Why would I want to hurt you?” the older woman purrs, her voice dripping with menace.

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It’s hard to think of a more ideal director to capture Shirley’s fragile state of mind than Josephine Decker, whose last feature, “Madeline’s Madeline,” was an overwhelmingly visceral and astonishingly empathetic portrait of mental illness. “Shirley” is drawn from Susan Scarf Merrell’s novel – a fictional account, but inspired by the period in which Jackson wrote her second book, “Hangsaman,” which was itself inspired by the real-life disappearance of a Bennington student. These are the kinds of interlocking levels of reality and storytelling we’re dealing with here. 

One of the masterstrokes of Sarah Gubbins’s screenplay is how deftly she underscores the differences in the perception and presentation of the sicknesses within this marriage. Stanley—played by Stuhlbarg as a big, gregarious bear of a man, his beard as overwhelming as his manner—is clearly just as troubled as his wife, but his illness and hostility are better concealed under a sheen of cheerful “eccentricity.” They’re a mess, a combustible combination; he’s a master of passive-aggression, while she spirals at the drop of a hat. 

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Yet Rose and Fred, this new, seemingly well-adjusted couple—they’re young, they’re gorgeous, she’s pregnant, they still lust for each other—becomes the stick of dynamite. Decker and Gubbins skillfully shuffle the complicated, shifting dynamics in this four-handed relationship (the echoes of “Who’s Afraid of Virginia Woolf” cannot be accidental), as Fred grows distant, Stanley becomes prickly (well, pricklier), and Rose goes from Shirley’s caretaker to her co-conspirator. They talk up storms, but there’s a world of words that live in their pauses, and a lesser director might lose the thread in the shifts from anger to resentment to eroticism. Decker doesn’t skip a beat. 

I’m not quite sure how Moss continues to find variations and nuances within the realm of mental illness, but she does. This character is both familiar from “Her Smell” or “Queen of Earth,” and entirely different. The things she’s doing here are quietly astonishing (watch for the moment when she stops herself from giving Stanley even the momentary satisfaction of her smile), and it’s undoubtedly the showcase, show-off role. But Young’s work as Rose is the glue that holds the picture together. Her journey from open book to a cauldron of secrets is tricky and exciting.  

Cinematographer Sturla Brandth Grøvlen bathes the early scenes in a warm summer glow as if they’re a fond memory, and Decker lulls us into complacency with late-night scenes near open windows, where the only sounds around are chirping crickets and whispered secrets. But those calming sounds and images soon curdle into nightmarish visions of blood and terror. As with “Madeline’s Madeline,” Decker has an uncommon gift for getting us into her characters’ heads via smeary, discombobulated compositions and complex soundscapes (the driving, nervous score is by Tamar-kal). This visual and aural shorthand for mental illness proves equally effective for creating the fugue states, false starts, and jagged rhythms of the writing process. 

If “Shirley” is not quite as emotionally devastating as “Madeline’s Madeline,” we might look to the question of authorship; Decker co-wrote that film as well as directing, and it seemed, in places, ripped from her very soul. But that’s not to imply that “Shirley” is merely some gun-for-hire job; it’s a spellbinding picture, and another fine vehicle for the strange and beautiful way this singular artist sees the world. [A-]

Follow along for all of our coverage from the 2020 Sundance Film Festival here.