Thrax holds an evil meeting in which he highlights his successes as a viruses. He illustrates that viruses can cause sickness and even be lethal. Jones, the white blood cell, asks if there is anything he can do to stop the virus, indicating that white blood cells (also known as leukocytes) protect the body from illness, disease, bacteria, and other foreign invaders.

With the help of the white blood cells, the StoryBots find the ability to combat a virus.

An alien has taken control of the ship, and the crew need to fight it. Spock explains the situation in terms of biology: the ship is the body, the crew are the blood cells, and the alien is the virus.

The Commander T-Cell informs all cells about pneumococcus on the loose and dispatches the Killer T-Cells to hunt them down.

Ralphie's class enters his body to find out what is making him sick. His classmates find bacteria cells in his throat and watch the white blood cells battle the bacteria cells. This clip illustrates the function of white blood cells: to fight infection and disease.