What role do dreams play in In Cold Blood?
There is a repeated emphasis on dreams in this novel. There are actual dreams and then "dream" can be seen as goal or aspiration as well. Perry has the dream of travel, going to Mexico, and seemingly being a the successful man that he is not. Perry also has the actual dream about the yellow parrot. This dream allows him to gain some sort of revenge on those who've hurt him over the course of his life.
Al Dewey's wife also dreams of Bonnie Clutter. Later, Paul Helm has an almost dream-like vision of Bonnie at the window of her bedroom, but it turns out to be a vagrant armed with a shot gun. Most of the dreams in the book end up like Paul's "vision"; an idea of something better that, in the end, never comes true as we hope.