Therese is an update of a 19th century novel by Émile Zola, set in mid 19th century France. The updates essentially consist of showing things merely implied in the original version, namely the sex and violence. Still, neither is done in explicit fashion.
The movie begins with Therese (Olsen) being dumped in her aunt's lap. Her mother is dead and her father has no idea what to do with her while he's gallivanting around Africa. She's close in age to her cousin Camille (Felton), who is sickly, weak, and doted upon by his mother (Jessica Lange). The kids grow up, and Camille's mother arranges for the marriage of the two cousins.
Therese is certainly not attracted to the idea of marrying her wheezing, sniveling, pale faced cousin. However, she is also made aware that, while she is a pretty young woman, she lacks the connections, money, or social standing required to bag another man. Meanwhile, no one else would have Camille either. It's a match made in heaven - what could go wrong?
Enter Camille's friend Laurent (Oscar Isaac), who Therese finds attractive, alluring, and doesn't seem to mind sleeping with his good friend's wife. Things get hairy when they decide to take their relationship past the affair stage and into the "get rid of the wheezer" stage.
The first couple acts seem to set things up pretty well, with nice comedic moments. In one, there was a new take on the tried and "hide the secret lover under the bed" scene. Other good bits were provided by the supporting cast, which includes Shirley Henderson and another actor whose name is frustratingly missing from both the festival guide and imdb. Check back with the latter and see if they've updated the page.
The film falls apart a bit in act three, with the characters' actions seeming a bit random. Lange is great down the stretch, and the final scene isn't bad, but I can't forgive how the film gets there. Perhaps they'll clean it up a bit in the editing room before the release. My imdb rating: 6/10.