The government's top agent is missing, and Jimmy Neutron has been recruited to find him. The boy genius goes across the world to find Agent X, who turns out to be Jimmy's super-spy hero, Jet Fusion. While rescuing Jet from his captors, Jimmy comes face-to-face with his old enemy, Professor Calamitous, who is determind to flood the world. Jimmy and Jet team up to defeat the evil professor, but can they stop him in time?