The chapter opens with a description of influenza, a disease that infects the body. It is caused by a strain of Streptococcus pyogenes, a bacterium that lives in the stomach. The chapter begins with a discussion of the role of the white blood cell in the defense of the body against infection. White blood cells destroy the body's own cells, but they also destroy those of other cells, such as those of the dendritic cells. The dendritic cells take in fragments of bacterial and virus-infected cells and present them to other cells as antigens for the immune system. When the chapter ends, the narrator tells us that he is sorry for the way the chapter ended.