What is the theme in The Monkey's Raincoat by Robert Crais?

Violence and war is another theme in this book. Elvis Cole and his partner Joe Pike are soldiers and warriors. They have both served in the Vietnam war and despite the horrors that they experienced there, they have embraced a life of violence. They approach their activities as private investigators as soldiers instead of as private citizens. Joe Pike describes himself to the police as a mercenary, and he acts as a mercenary much more than as a private investigator.