What are the motifs in Double Indemnity by James M. Cain?

Evil in the ordinary is a theme in the story. What could be more ordinary than an insurance salesman making a call on a client? What could be more ordinary, albeit somewhat empty, than Walter's life? What could be more ordinary than a "housewife" talking to a sales representative about products offered for sale? It happens every day, all across the country. Yet in Cain's world view it can be these types of seemingly ordinary situations and events that lead to evil deeds.