Cathy Jamison, having already bought her son a car he'll never know about, has decided to teach Adam to drive. Or at least to give him preparatory lessons. As one might have predicted, this goes poorly -- "Do you know how many children are run over every year because people don't do their one-two-threes?" -- and before they've left the driveway, their nerves are already jangling. Paul approaches, shouting at them, at Cathy; he doesn't understand her hurry.
"I'm not allowing him to drive, I'm teaching him how to drive," Cathy explains. "I just thought we'd get it over with." Cathy wanted to be the teacher here, because Paul is not a great driver, but saying so only makes him more belligerent.
"Okay, you teach him how to drive, I'll teach him how to run off to the Bahamas!" A valid point, in a way, but it gets her hackles up enough that Adam orders them both to stop fighting, and they apologize. "This isn't fun for me," he says as he's leaving; the quieter implication is that, in some way, it's fun for them. Maybe he's right.
Paul admits he can't talk to her, anymore, without blowing up at her, and explains his presence away as more than the usual trumped-up excuse to come home: A promotion to VP, for which he has been waiting a while. Cathy's excitement over this, something they waited so long for, is not something she can contain. She maybe having an affair, she may have tossed him out for reasons that revolve from blurry haze to sharp clarity every few minutes, but this is something they planned for, together. She beams at her husband, congratulates him, wonders if he'll want -- if he'll need, she clarifies, because that sounded too much like begging -- any company for the dinner.
Not after her birthday disaster, he won't. "What, so you can suck all the joy out of that moment for me too?" He shrugs: This only proves his point that niceness is currently beyond his abilities. This celebration covers the unhappy twenty years, he means, that she has hated her life with him. It's too long a story to retell, or explain; his story isn't something she can rewrite.
Ever since he left the house Paul Jamison has been writing and rewriting it, polishing it, making it shine, taking every evidence she gives and discarding the rest: The story of Paul the victim. He employs a therapist, and his sister, and even Cathy herself, in order to add more and more sumptuous details, to make it all the more vivid. What this does is give him a complete lack of accountability for his own life; the reason Cathy did it, of course, is that he's always had that.