Have you ever wondered what happens inside your body when you're sick? That's the only question on twelve-year-old Alex's mind when he catches a nasty cold on the biggest day of his life, the day of the sixth-grade science fair. His dreams of competing and beating his arch enemy, Zoey Perez, are in danger. But as the day begins, Alex makes an amazing discovery - his dad, Frank, is a superhero!

Frank becomes Micro Dad, a hero with the power to shrink to the size of a microbe and do battle with the unpleasant, bad-tempered, cold virus, known as The Rhino and his army of germs, who want nothing but to destroy Alex. Micro Dad must travel through Alex's body and team up with his white blood cells to defeat The Rhino, save Alex and get him to the science fair. It's a race against time. Can Micro Dad make it?