|Nancy explains that the diagonal line passing across the painting is the dream line. She says that the Mountain Devil, also known as the Thorny Devil, travels the dream line and as the Devil passes through night and through day, it changes colour. It is black at night and as the dawn breaks it changes colour. As the sun rises it becomes brighter, the devil changes colour to yellow. The colour changes aid the devil being undetected as he presses along the dream line.