Director/screenwriter David Gordon Green adapts Stewart O'Nan's popular novel to the screen in this feature, which tells the parallel tales of a teenager named Arthur (Michael Angarano) and his onetime babysitter Annie (Kate Beckinsale) -- whose turbulent relationship with her estranged husband, Glenn (Sam Rockwell), leads the small-town waitress down a troubled path. Arthur is a high-school student from a dysfunctional family, and does everything in his power to avoid hanging around the house while mom and dad quarrel. When he's not practicing his trombone and performing with the high-school marching band, Arthur can usually be found bussing tables at the local Chinese restaurant and flirting with older waitress Annie. Annie used to be Arthur's babysitter, and is currently struggling to separate from her former high-school sweetheart, Glenn. But being a single mother isn't easy, especially since the troubled Glenn wants nothing more than to clean up his act and reunite his family.
Back at school, Arthur and pretty classmate Lila (Olivia Thirlby) have been bonding over their mutual love for all things geeky. Though the casual friendship shows promise of evolving into something more when Lila expresses her true feelings for Arthur, he can't help but becoming distracted by his chaotic family life: his father is moving out of the family home, and his mother is doing everything in her power to maintain some semblance of normalcy. Realizing that happiness is fleeting as his family becomes shattered and Annie experiences a series of distressing encounters with Glenn, Arthur gradually begins to fall for Lisa despite his growing cynicism concerning long-term relationships. Later, on a cold winter morning, Glenn and Annie's past catches up with them in a blinding flash, and the lives of everyone they know are suddenly and irrevocably changed.