Barbara Covett (Dench), a longtime instructor at one of London’s secondary schools, yearns for friendship with Sheba Hart (Blanchett), the beautiful new art teacher. When she discovers Sheba’s affair with a teenage student, Barbara realizes this knowledge can be the ticket to achieving her goal.

“I’ve known several people like her,” Dench says about the character she plays. “A very, very lonely person who craves affection and to have any friend of some kind. I think there are a lot of people out there like that who have been lonely all their lives and dream of friendship. But when Barbara essentially blackmails Sheba Hart into becoming close to her, that’s when things go awry.”

It may be a shock for Dench’s fans to see her in this very different type of role. Barbara is definitely not a nice woman. She’s selfish, manipulative and dangerous. However, by endowing her character with a poignant vulnerability not easy to ignore, Dench manages to make us feel somewhat sorry for Barbara. This is a fearless performance, one requiring Dench to convince viewers of Barbara’s disturbing behavior and unattractive appearance. Fortunately, she succeeds completely. It becomes abundantly clear that with a friend like Barbara, you don’t need enemies.

In contrast to Barbara’s solitary life, Sheba seems happily married, although to a much older man (the versatile Bill Nighy). She’s spent the past few years caring for a son who has Down Syndrome. After taking a position at the school where Barbara teaches and befriends her, Sheba soon learns that one of her students (Andrew Simpson) has a crush on her. Why does she give in and throw herself into a sordid, illegal affair with this cheeky teenage boy? According to Blanchett, Sheba feels she’s “whittled away her youth,” so she’s trying to recapture it.

Guess I’m channeling the Church Lady again, but that reason isn’t good enough for me. Even though Blanchett is always a treat to watch on screen, her character’s actions here come across as more soap-operish than realistic. Of course, she’s lovely to look at and projects a wonderful feeling of abandon as she becomes more and more obsessed with her young student -– but I don’t believe this is her best work (“Veronica Guerin” is my favorite).

Based on the popular novel by Zöe Heller and directed by Richard Eyre (“Iris”), Notes on a Scandal benefits from a powerful background score by Philip Glass (“The Illusionist”) and an involving screenplay adaptation by Patrick Marber (“Closer”). Although not at all pleasant to watch (I was hoping for at least some humor, perhaps similar to the kind featured in “To Die For”), this haunting film is a memorable portrait of self-destruction and shame.

(Released by Fox Searchlight and rated “R” for language and some aberrant sexual content.)

Review also posted on ReelTalk Movie Reviews.