Jennifer Aniston is Justine, the title character of THE GOOD GIRL. Justine, though, is no longer a girl - she is grown up, married and longs to start a family. Without a doubt her husband, Phil (John C. Reilly) loves her, but they have so far been unable to conceive, and Justine wonders if all the pot he smokes with his best friend Bubba (Tim Blake Nelson) might be the reason why.
One day at work, Justine discovers something of a soul mate in Holden (Jake Gyllenhaal), a creative, passionate young man who represents a chance for Justine to escape into a new world of emotional and sexual awakening. But when the affair quickly moves from liberation to poisonous obsession, Justine finds herself ensnared in a chaotic web of blackmail, larceny and love.
Is Justine ultimately a good girl? Can she make the right choice between her dependable husband and disturbed lover?