BC12, a red blood cell, lives and works in a body that is currently struggling with dehydration. He is given the task of traveling to Brian, the brain, and convincing him to drink some water. BC12 sets off on the journey and encounters various organs along the way, all of which have an opinion (sometimes more, sometimes less helpful) about Brian and his passivity. Finally arriving in the head, Brian and BC12 bond over their goals, failures and chaotic emotions. Brian finally fulfills BC12's great desire to see the outside world by giving their body a nosebleed and finally drinking some water.