Where was Brian going and why was him in a plane?

The book begins with thirteen-year-old Brian Robeson flying as a passenger in a small bush plane from Hampton, New York. He is on his way to spend the summer with his father in the Canadian wilderness—his parents recently got divorced, something that has taken a toll on Brian. While in the plane, he thinks a lot about the divorce and about a particular secret that he calls The Secret. He believes it is this secret that caused the divorce.