Spirituality is the key to events throughout The M.D. Early on, Billy learns that he can see aspects of life that other people cannot; if he concentrates and looks just right, he can see a little of the spiritual world that is always active and infusing itself into human experience.
This makes him special, and for much of the novel it seems that this is why Mercury is drawn to him. But the spiritual realm is a complex place, and it turns out that Billy did not influence Mercury, that instead Mercury created Billy through generations of genetic manipulation......
