In the middle of the night, somewhere in Oklahoma--or is it Missouri?--a bus hurtles down an anonymous American highway. Its passengers, among them two children traveling on their own, a retired salesman, an unwed teenage mother, an unemployed chemist, and the driver who ferries and broods over all of them, are in the middle of their journeys. Soon, two of the passengers will be lost, and then the bus itself will lose its way.