After botching the first invasion, invader Zim is eager to redeem himself to the leaders of his home planet Irk. They assign Zim an obscure, unimportant planet called "Earth" along with his sidekick Gir. Together they infiltrate human society disguised as a schoolboy and pet dog. Strangely, no one at "Skool" seems to notice him except for classmate Dib, who's an obsessed paranormal investigator. Dib tries to warn the world, but no one believes him except his sister Gaz, who doesn't care. Clueless but relentless, Zim roams Earth looking for weaknesses in our defenses and the big break that will win him praise and recognition from his leaders.