It's more than a little unfair to compare Natalie Portman to Kristin Scott Thomas, but I'm sort of going to do it anyway. Really, though, I'm comparing their movies (both of which have infidelity as a theme, and both of which are in Toronto in hopes of studio acquisition), and how a single performance transforms everything around it.

Portman stars in Don Roos' "Love and Other Impossible Pursuits," in what the festival is touting as her first grown-up starring role; she plays a young attorney and second wife grieving the loss of her infant. Nothing about this film rings true, starting with the way Portman's character is written: We're supposed to sympathize with her, because she's the heroine and because she's lost a baby, and yet she's insufferable. We watch her deliberately seduce a married colleague, then, after she's married him, whine incessantly about how the mean old first wife hates her (hmm, you think?) and treat her eight-year-old stepson mostly with contempt. Perhaps a warmer, more skilled actress could have made something of this (maybe), but Portman's performance is on-the-surface glamorous yet flat-voiced, teenagy and ineffective. I wish Roos, who made the very funny "The Opposite of Sex" a while back, much better luck with his next film.

And then I saw "Partir" ("Leaving"), a French drama by Catherine Corsini about a woman (Scott Thomas) who leaves her wealthy husband for her working-class lover. Suzanne is also a character with whom it's hard to sympathize -- she seems to have few qualms, for example, about leaving her children behind -- but Scott Thomas's remarkable performance sweeps you into the film. This lovesick woman has been shot by a bolt from the blue, and she seems powerless in its wake; Scott Thomas plays Suzanne as one thin, raw nerve, trembling in the force of her emotions. Though a few in the audience giggled uncomfortably at the film's almost melodramatic turns at the end, I was completely taken by this portrait of a modern Emma Bovary; the film seemed over in a heartbeat, while "Love and Other . . ." seemed to go on forever. So be it.

A reader asked earlier about Lars von Trier's notorious horror drama "Antichrist": yes, it's here, and no, I haven't seen it, mostly due to scheduling ("Antichrist" screened at the same time as a film I had to see for an interview) but also due to von Trier fatigue. (I've hated his last few films.) People here are definitely talking about the shock factor of "Antichrist"; even the staid program guide says "If you think you're prepared for some of the now notorious graphic sequences, you most assuredly are not." But I haven't yet heard anyone say they really liked it; more common is the reaction I heard this morning in line, that the film was "pretentious for pretension's sake." It'll be in Seattle this fall, so we can all make up our own minds.

And one final celebrity note: Crowds were huge around the Four Seasons today, and I asked a very female and very young group who they were waiting for. Of course: It was the Jonas Brothers. And why are they here? No idea. Later I asked a bored-looking cop if he'd had any celebrity sightings; he just sighed.

Off to dinner with George Clooney (and some other people). Supposedly. Stay tuned.

(Photos: Natalie Portman in "Love and Other Impossible Pursuits." Courtesy of Toronto International Film Festival. Kristin Scott Thomas at TIFF. By AP Photo/The Canadian Press, Chris Young.)