I want to believe!

Jesus comes down off the mountain to a furore. His Disciples have failed to drive out a demon from a little boy and the crowd are not impressed. The Disciples are confused and down-hearted. Why could they not drive out the demon when they could do so just a short while before? The response of Jesus and his explanation to the Disciples of what they were doing wrong contains a challenge that is just as relevant to us today as it was back then. Based on the text of Mark chapter 9.