The British Empire had many purposes, but in fiction it existed as mostly a place to test, and perhaps transform, hardy expatriates. At home, the sort of characters who battled for their souls in China, India, or other British fiefdoms could expect nothing more profound than drawing-room comedies. That schema is a bit dated, but as The Painted Veil successfully asserts, not entirely outmoded. For all the physical dangers evoked by this period drama, however, it never feels as threatening as the stunningly venomous Notes on a Scandal, which doesn’t venture anyplace scarier than a North London secondary school.

Adapted from Zoë Heller’s novel, What Was She Thinking?: Notes on a Scandal, the film observes a pathological friendship between two teachers, frumpy Barbara Covett (Judi Dench) and glamorous Sheba Hart (Cate Blanchett). There are other relationships in the story, but they’re all Sheba’s—which is precisely the problem. The steely, older Barbara, who teaches history to kids she calls “proles,” is more assured in the classroom than Sheba, a newly arrived art instructor. Away from school, however, Barbara is desperately needy. When free-spirited and somewhat silly Sheba begins an affair with a 15-year-old student that threatens her marriage and her career, Barbara couldn’t be more delighted. If Sheba’s life is destroyed, all the foolish newcomer will have left is her new mentor.

Barbara is introduced on a park bench overlooking her little world and musing on her special gift: “People have always trusted me with their secrets.” Those confidences are divulged to her notebook, and nowhere else, provided that her advice is followed to the letter. So when Barbara ducks out of a funky version of “Hark, the Herald Angels Sing” at the school Christmas pageant and finds Sheba having sex with beautiful but rough-edged Steven (Andrew Simpson), the older woman is all business. Barbara informs Sheba that she’ll say nothing, providing that the affair ends. When she later learns that it hasn’t, Barbara sets her plan in motion. Soon, Sheba will lose Steven, husband Richard (Bill Nighy), and their two children, a sulky teenage girl and a boy with Down syndrome. Barbara gets exactly what she wants—but only temporarily.

Director Richard Eyre (Iris) and scripter Patrick Marber (Closer) tell this story with a minimum of flash; the only overstated element is Philip Glass’ score; as they did in The Hours, the driving ostinatos overwhelm the gentle rhythms of chamber drama. Where the dominant key of Closer was candor so cruel as to be unpersuasive, this time Marber adopts a more traditionally English tone: self-delusion. Sheba has a few moments when she’s brought up short, notably one in which she overhears her mother opine that Sheba lacks “substance,” but mostly she imagines that she can do what she wants and that everyone wishes her well. She’s manipulated by both Barbara and Steven and relies heavily on Richard (a forceful performance from Nighy, who’s known for comic roles) without entirely realizing it. Still, the flitting Sheba is less baffled by life than is the coldly centered Barbara.

“One soon learns that teaching is crowd control,” Barbara informs Sheba, a much harsher outlook than that of The History Boys (which also goes easier on the notion of teacher–student sex). The veteran imagines that she has control, even when she must know she doesn’t (e.g., the story of her former colleague Jennifer, which is eventually revealed to be rather different than the version Barbara tells). The master plotter denotes especially satisfying events by placing gold stars in her diary—one of the film’s few overly contrived touches—and revels in her own manipulations. As her plot is on the verge of unraveling, Barbara can still write, with great self-satisfaction, that “this last month has been the most delicious in my life.”

Dench’s characterization is indeed delicious, a gallery of fleeting gestures and a survey of quicksilver shifts in emotion. A half century ago, her Barbara would have been the predatory lesbian, and Sheba the entrapped innocent. But Eyre and Marber are more nuanced than that, showing both characters’ frailties, and not precisely defining their friendship. Certainly Barbara is in love with Sheba, in a way, but what she wants from the younger woman is not entirely clear—even to herself. Notes on a Scandal ultimately reaches a resolution worthy of melodrama, but its psychological insight belongs to a far subtler genre.