How does the author use foreshadowing in From the Mixed-Up Files of Mrs. Basil E. Frankweiler?

In the opening pages of the novel, Claudia is aggravated that she once again has to watch over Kevin. Kevin, also aggravated, tells Claudia that he wishes it was his brother's turn to watch him.... not Claudia's. Claudia's response, 'You just may get your wish...' foreshadows Claudia running away from home.