Young girl Tracy lives in New York and studying at a local college, but her student life cannot be described as colorful and eventful. The heroine of the movie "Mistress America" quiet and lonely girl who don't have fun at parties, no twists novels with different guys and not experiencing exciting adventures with friends. In the life of Tracy all calm and monotonous. It is calm disturbs news from his mother about her impending wedding, after which Tracy appears stepsister Brooke.
But Tracy doesn't know about that encounter with Brooke will change her life, and not for the worse. Sociable, energetic, dedicated and cheerful dreamer Brooke is going to open his own restaurant, but loses the main investor in the face of her boyfriend. Without dropping hands girl looking for solutions to the problem, pulling a consolidated sister in the maelstrom of exciting adventures.