What is the primary source of suspense in this chapter

This is the scene of the actual con-job that the duke and the dauphin pull over the Wilks family. They have realized there is even more money than they thought at stake. They make quite the spectacle of their sorrow and "generosity" to the family. Doctor Robinson, a family friend, points out that both men are frauds. The duke and king have to put on a real show to overcome this.