Published in 2003, Zoë Heller's epistolary novel What Was She Thinking? (Notes on a Scandal) is a juicy update of John Fowles' 1963 classic The Collector. In fact, Heller's "heroine," the superbly named Barbara Covett, could be a relative of Frederick Clegg, the amateur entomologist and painfully shy suitor who kidnaps the young woman he worships from afar and locks in his basement in a misguided attempt to win her heart. Barbara doesn't go to such extreme lengths to woo the object of her desire, fellow public school teacher Sheba Hart, but in a way her methodology is even more disturbing. Her first step is to maneuver herself into the position of being her colleague's closest friend and confidante. Then, as Sheba begins to feel more and more comfortable around Barbara, she lets certain secrets slip, like the fact that she's developing feelings for one of her students, a 15-year-old named Steven Connolly. Like any good friend, Barbara immediately advises Sheba to cease contact with the boy, but as she later discovers, the affair has progressed well beyond mere flirtation. Though Barbara claims to be upset, it's clear that she's thrilled to be in possession of such an important secret, as it only gives her more leverage over her target. As she chillingly writes in her diary, "Sheba is my friend. She needs me now."

It should be noted that there is one crucial difference between Clegg and Covett. Where the former seeks true love, the latter simply desires companionship. Heller makes it very clear that, while there is a sexual component to Barbara's pursuit of Sheba, her overarching goal is to have someone, anyone, to fill the void in her life where another person should be. And that's the first and most important thing that the movie version of Notes on a Scandal gets wrong. In translating Heller's book to the screen, screenwriter Patrick Marber, best known as the author of Closer, has opted to play up Barbara's repressed sexuality, to the point where she often comes across as a lesbian predator out to ensnare the poor little straight girl. It's a baffling choice, particularly in an era when we've supposedly moved past such demeaning stereotypes of unmarried women of a certain age, not to mention lesbians. Of course, one could make the case that Marber intended Notes to be played as a dark comedy, in which case no one bothered to inform director Richard Eyre, who displays the same leaden touch here that he brought to his previous feature, the overpraised Stage Beauty.

As is their prerogative, Eyre and Marber have made a number of other significant changes to the novel. Some of their modifications are effective, such as the decision to have Barbara learn about Sheba's affair much earlier in their friendship. In addition to compressing the timeline, it gives Sheba more of a reason for keeping this bitter crone happy. They were also wise to jettison a subplot involving Sheba's bratty teenage daughter, which came dangerously close to being too over-the-top even on the page. But many of the other changes are poorly conceived and executed, including the way Sheba and Connolly's affair comes to an end and the precise reason that Barbara allows Sheba's secret to escape out into the world. Worst of all is the horrid new finale, which not only feels like a copout, it fundamentally alters the point of the story.

If there's any reason to see Notes on a Scandal instead of simply giving Heller's book another read, it's to watch two superb actresses doing their best to hold the rickety contraption together. You couldn't ask for better casting; although Dench has played countless sharp-tongued old ladies during the past decade, this is the first time in years (possibly since her acclaimed turn as Lady Macbeth in a highly lauded 1979 TV production of Shakespeare's Scottish Play) that she's played a true villainess. Likewise, Blanchett is one of contemporary cinema's great beauties, but she rarely has the opportunity to play an overtly sexy character. Together, these two pros offer a master class in carving strong performances out of subpar material. Bill Nighy also does some nice work as Sheba's clueless husband, but once again, that character's story arc has been so completely altered from the book that some of his best scenes are missing. It's a shame that such a deliciously twisted story comes across as so pedestrian onscreen. At least Heller can take some comfort in knowing that the movie version of The Collector didn't really live up to the novel either.