What is the main conflict in A Wild Sheep Chase by Haruki Murakami?

Over the course of the novel, the man, who is an advertising agent, finds himself as the recipient of a photograph from a friend, the Rat. After using it in an advertisement, the man finds himself bent to the will of the Boss, an underground right wing shadow figure who runs much of the political, financial, and social empire of Tokyo. The Boss is dying and sends a messenger to inform the man that he has one month to locate one of the sheep in the photograph, or he will be financially ruined, at best.