Zach is riding the Greyhound bus through a snowstorm to visit his older brother Derek, whom he hasn't seen in seven months. That's when their parents finally went broke paying Derek's doctor's bills and had to give him up as a ward of the state. Nothing—not drawing in his sketchbook, not basketball—lets Zach forget that his brother is living in a mental institution five states away. But surprisingly, sitting next to a talkative teenage girl he nicknames Purplehead starts to take the edge off Zach's pain.

Prompted by a chain of unpredictable events and by the people he meets along the way, Zach's cynical humor gives us a poignant look at medical insurance and health care systems for the mentally ill, and at the everyday fears, joys, and revelations of adolescence.