Who is the boy that helps Julia's husband cope with his life?
Davis is a successful investment banker at a firm founded and run by his father-in-law Phil. His wife, Julia, is driving them when they are struck by another vehicle, killing Julia. Recovering in the hospital, he attempts to purchase some candy from a vending machine which malfunctions. Davis drafts a complaint to the vending machine manufacturer that includes some venting of his personal experiences. This leads to a series of anonymous conversations with a customer service representative, Karen Moreno, in which they end up sharing details of each other's life burdens.  Karen appears to be the only one he talks to, though tells his stories in an understated and unemotional style.  He brings this same unemotional process to work, which he has returned to much earlier than anyone expected.  Davis does tell one other person, a fellow commuter train rider that he realizes that he didn't love Julia because he doesn't feel "...sad, or pain, or hurt...".
Davis's changing emotional state causes him to behave erratically. He notices that he is being followed by a green station wagon. The only thing Davis seems to connect with is trying to understand what's inside things, using a small toolkit to dismantle his household appliances, his work computer, a bathroom stall—eventually telling Phil that he has an urge to dismantle a 120-year-old grandmother clock in Phil's office.
Karen follows Davis, talking with him on his commuter train without revealing her identity. She mistakenly leaves some identification, and Davis is sufficiently moved to track her down at home, where she lives with her boyfriend and boss, Carl, and her 15-year old troublemaker son, Chris.  When Carl goes on a long business trip, Davis bunks at her house, where they develop a deep platonic friendship. Chris initially dislikes Davis, but later grows not only to like him but to help Davis cope, while Davis becomes his mentor in return.
Chris