The StoryBots take a trip to the lymph node, where they speak to a white blood cell. They learn about the role that the white blood cells play in protecting a person's body against viruses.

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.

Beakman explains what allergies and allergens are. He talks about how the immune system causes the allergic reactions through the production of histamines. He uses a clip to show how a sneeze happens physiologically.