Inside a human's body, roughly 37.2 trillion cells work hard everyday endlessly to keep their host healthy. Red Blood Cell, a new, ditzy Red Blood Cell was attacked by a group of Pneumococcus Bacteria during the midst of her job. Then White Blood Cell, a neutrophil appears and ruthlessly terminates the Bacteria before they could do any harm. Red Blood Cell thanks White Blood Cell for saving her and they part ways.
As Red Blood Cell wanders around looking for the lungs, she decides to check the map and enters the map room. However, when she opens the door, she finds a Pneumonia Coccus, who's also looking at the map. Then the two are surprised and then Red Blood Cell closes the door, only for the Pneumonia Coccus to smash the wall down and yell at her for pretending as if nothing happened. Then White Blood Cell finds the two and battles Pneumonia Coccus, but then the Pneumonia Coccus escapes by tossing a bacterial shell to create a smokescreen and pin White Blood Cell down.
Then White Blood Cell offers to take Red Blood Cell to the lungs, which she accepts. With the threat of the lungs being infected, Helper T Cell authorizes the Killer T Division to hunt down the bacteria. Then the Killer T Cells mocks Red Blood Cell and then White Blood Cell tells her not to pay any attention to them. Then they cut their way through the Dendritic Tree to take a shortcut to the lungs. However, they find the tunnel closed and then a Platelet informs them that because of unforeseen circumstances, no one can pass. Then they noticed that the platelets are struggling to open the cargo boxes as they're too short, so, they assist them and then they're allowed to go through. On the way, Red Blood Cell notices White Blood Cell's receptor's acting strangely, and then he states that it goes off whenever a virus or bacteria's nearby.
Then they arrive at the lungs where they part ways. Then White Blood Cell notes that his receptor has stopped shaking violently, and realizes that something's not right there. Then the Pneumonia Coccus bursts out of the box Red Blood Cell was transporting, and then he thanks her for giving him a free ride to the lungs. Then he causes havoc, but White Blood Cell quickly intervenes and states that he realized that he was hiding in the box after Red Blood Cell left. White Blood Cell's unable to kill the Pneumonia Coccus because of his bacterial shell, so, he lures him into the respiratory tract. Not realizing what he's up to, the Pneumonia Coccus steps onto the red line and triggers an alarm; then White Blood Cell presses a button, and then the bacteria's trapped in a bubble. Then the two cells take some tea and watch as the bubble's deposited into a missile and ejected from the body as it sneezed, and then they went their separating ways.
- Around the end of the episode, when the captions read "Incident! It's Bacteria! They're close!", the receptor from U-1146's hat disappears for a frame/split-second.
- For a moment after the main platelet apologizes, the team's sign is shown to be behind the striped caution sign. But in the next shot, the platelet sign is in front of the caution sign, and closer to the main platelet.
- After White Blood Cell and Red Blood Cell got their tea, his glove looks like it's missing.