Going in, Linklater knew the general outline of his story, but he didn't know that 9/11 would happen, or that Lady Gaga would become famous, or that Ellar Coltrane, who plays the central character, would become a handsome teenager. The most poignant aspect of movies has always had to do with time, the way film seems to stop time but can't - because nothing can. Mason is a 6-year-old, living with his divorced mother and his precocious 8-year-old sister, Samantha (Lorelei Linklater, the director's daughter), who loves to torment him. The dramas are the dramas of daily existence, not movie-scale drama, but then, normal life offers enough stress: the tension of listening to Mom and her boyfriend argue in the next room or the agony of uprooting from one city to another. In one scene, as Mason and his family drive away forever from the house he grew up in, he looks out the car window and sees his best friend, in the distance, riding a bicycle, and you get the full impact of that moment. Hawke talks to the kids with the same energy and enthusiasm that he brings to his conversations with Julie Delpy in the "Before" movies. There's an excruciatingly embarrassing scene between the father and his 15-year-old daughter, in which he tries to advise her on the subject of contraception while she buries her face in her hands and cringes. Watching Arquette here is like watching a generation's hopes and struggles, presented by an actress with a fullness of emotion, and yet with utter matter-of-factness.