At first, Atom Egoyan's Chloe doesn't seem any different. Catherine (Julianne Moore) plans an elaborate surprise birthday party for her husband David (Liam Neeson), but he calls at the last second to tell her that he's missed his flight home. The next morning, following his return, almost by accident, Catherine finds a text and accompanying photograph on his phone indicating that he missed it on purpose, and spent the evening with a pretty young woman instead. Catherine is a gynecologist, and she reassures a patient that an orgasm is "just a series of muscle contractions", but David's unfaithfulness eats away at her, morphing each charming compliment he offers an attractive waitress into a slimy grab for sexual attention, and twisting each appearance of her son Michael (Max Thierot) and his sexy young girlfriend to be a painful reminder of what she doesn't have.

Desperate to confront David but unable to summon the words, Catherine seems to be at a loss for what to do until opportunity arrives in the form of Chloe (Amanda Seyfried), a prostitute who Catherine hears crying in the stall next to her, in the bathroom of the restaurant with the pretty waitress. Catherine cheers her up and walks out, but the next day, she tracks down and hires Chloe to tempt David. Almost immediately, Chloe returns and informs Catherine that David is indeed cheating, and on an emotional level, Catherine begins to unravel.

Many movies would only allow Catherine one of two reactions -- hatred and perhaps revenge, or overwhelming sadness -- but Egoyan and writer Erin Cressida Wilson find a different route. Catherine still loves David, and is blown away by Chloe's vividly incriminating, detailed descriptions of her and David's trysts. At the heart of all of Catherine's reactions is an understated combination of envy and crumbling confidence: what do these girls have that I don't, and how can I get my husband's attention back? One of the most interesting developments is how Catherine lives vicariously through Chloe's descriptions of the sex she has with David, and the tinge of guilt she feels, knowing that the only way she can think of to reconnect with her husband is to do it through the girl he's sleeping with instead. Catherine's desire for whatever Chloe has that she doesn't quickly morphs into a need to keep sending Chloe after David, and in one of the more well-publicized scenes in the film (which I won't explain, in case you've managed to avoid it), things take a drastic turn. When the dust settles, Catherine suddenly sees how far things are spiraling out of her control, and finally moves to take action.

Unfortunately, though, her actions are the point at which Chloe hits a wall. Egoyan's ideas are better than his payoffs, and the events of the third act feel like they've come from a lesser movie. The web of desire and danger that the movie spins would be right at home in a B-movie, but the scale finally tips definitively towards the "schlock" side of things, especially in the hokey, disappointing conclusion. The performances by Moore and Seyfried are both entrancing at first (especially Seyfried, whose large, expressive eyes stare right through Catherine and into her soul, desperately trying to understand the emotional turmoil that Catherine is feeling), but neither actress can stay engaging when the script decides to abandon them; all of the interesting emotional facets of their characters just up and disappear. Meanwhile, Neeson's involvement almost feels like a side note (another problem of the writing, I think, and not related to his tragic personal situation during some of the shooting).

At one point, Chloe discusses her need for the "first date" feeling, describing the mentality of people desperate to make a good impression on someone they like and why that feeling fades, while Catherine tells David that "first we were lovers, and then we were parents, and then we were friends. And I didn't know how to go from being your friend to being your lover." Both of these are wonderful speeches, based around core ideas that are worth exploring, and their execution is good, even worth seeing the movie for. However, none of the things that happen at the end of Chloe have anything to do with either of them, and it renders the overall experience underwhelming. Egoyan and Wilson have latched onto more intriguing emotional threads than most other movies about infidelity, and they've assembled two powerful performers to give those emotions weight, but at the last minute, they've apparently exhausted the extent of their inspiration, and all that anticipatory suspense and sexual tension Egoyan effectively builds up through the entire movie just peters out.