Frank Detorre is the zookeeper at the Sucat Memorial Zoo in Rhode Island with a very disgusting and unhealthy lifestyle. Despite his daughter's advice, he eats very unhealthily, and eats a hard boiled egg that had been dropped in a chimpanzee's feces. Inside his body, Osmosis "Ozzy" Jones, a white blood cell who is determined for a little action, gets relocated to Frank's mouth to fight incoming germs. Soon, a virus named Thrax emerges from the egg Frank ate and plans to kill Frank with an infection posing as a common cold, with all the same symptoms. Frank's internal Mayor, Mayor Phlegmming is up for re-election although a lot of his actions are responsible for Frank's deteriorating health. Frank winds up taking a cold pill named Drixenol "Drix" who arrives inside his body and teams up with Ozzy. Ozzy and Drix must now team up to fight the infection before Frank slowly dies of it.