Ed and Connie Sumner are a middle-aged couple with an 8-year old son and a nice big house in the suburbs. They seem genuinely in love with each other even after 11 years of marriage. Ed runs his own trucking company; Connie does charitable fundraising which requires occasional commutes into New York City.
On one of these trips it is so windy that people are literally being blown around, and Connie collides with a young man named Paul Martel, and falls and scrapes her knee. Paul invites her to his apartment for a band-aid. This leads to a phone call and visit next time she is in the city, then trips into the city for the sole purpose of seeing Paul, and soon they are having a full-blown affair.
Ed notices the awkwardness in the relationship almost immediately, and his suspicions are further aroused when he catches Connie in a lie, and when a fired employee insinuates that there are things about Ed's family that he is not aware of. Finally he hires a private investigator, who soon furnishes pictures of Connie and Paul together.
Ed goes to Paul's apartment, and during the discussion that follows, he sees a gift he had once given Connie that she recently gave Paul. Ed loses his composure and hits Paul over the head, killing him. He then wraps Paul's body in a carpet, wipes clean everything he has touched, and cleans all the blood off the floor. While he is doing this, Connie calls and leaves a message on Paul's answering machine that she wants to end the affair. Ed loads the carpet with Paul's body into the trunk of his car, and later dumps it in a landfill.
Now it is Connie who senses awkwardness in their relationship. Cops visit investigating Paul's disappearance, because they found Connie's name and address in his apartment. Some time later, after the body is found, they come again. She is evasive, trying to conceal that she knew Paul at all, and the cops easily pick up the inconsistencies in her story. Ed surprises her by lying to the police to corroborate her story. After she finds the pictures from the private investigator, the two finally come clean with each other.
Ed offers to turn himself in, but Connie dissuades him, saying that they can get through this together and get on with their lives. The movie ends with the two of them in love with each other as they were at the beginning.