The story begins with a car full of people driving through the countryside, led by a man named Cal Damuth, who is eating burgers. His pregnant passenger, Becky, suddenly feels nauseous and they pull over, where she vomits. After reassuring her, Becky suggests they turn back, but Cal insists they’re already halfway to San Diego. Becky is anxious about what their parents will think since they’re siblings, but Cal tells her only her decision matters.