Based on a book series, this is the third and final movie of the Antboy trilogy, an offbeat superhero series that revolves around Pelle Nohrmann is a 12-year-old boy whom nobody ever seems to notice. This all changes when an ant bites him on the neck, and he begins to realize he has the strength and agility of an ant.
With the help of a comics-obsessed classmate, Pelle transforms into Antboy, a superhero who stops bullies and rescues those around him who are in distress. Pelle begins to use Antboy as a springboard to attain the popularity he never received before, especially from shrieking girls who worship Antboy, but, when a new, faster, more powerful superhero arrives on the scene, Antboy is insulted and teased once more, and wants to retire.
However, when a mad scientist known as the Flea takes a girl Pelle has a crush on prisoner because he feels wronged by the girl's wealthy father, Antboy/Pelle must find a way to stop the Flea and learn what it really means to be a superhero, including team up with the new superhero to defeat The Flea. Will he succeed in his mission?