Eleven-year-old Matthew introduces his family to his imaginary friend, a creature called Chocky, who is full of questions about space travel and gravity fields that are unlike any an eleven-year-old boy would ever think of. So when Chocky starts causing Matthew a great deal of distress - and questions at school - Matthew's parents find themselves forced to go to the professionals. But where does this voice come from? And what price will Matthew pay for his unusual friendship?