Rarely have broad themes such as "the blossoming of sexuality" and "the loss of innocence" been handled as carefully as they are here. Credit certainly goes to Dern, who shows incredible range while underplaying every massive change in her character's development, but much of the effect that the film has springs from its unusual structure. The first hour, seemingly observational, is designed to help us to understand what is threatened in the last act. Just when the movie seems to be heading toward an obvious statement, it opts for ambiguity and grows all the more powerful for the choice.