In Mission Critical, brother-and-sister team Juni and Carmen Cortez attend Spy Kids Academy, a top secret spy school for kid agents. When a new counter-spy agency threatens the safety of the world, it will be up to junior spies Juni and Carmen to train and lead a team of fellow Spy Kids cadets against the forces of S.W.A.M.P. (Sinister Wrongdoers Against Mankind’s Preservation) and their diabolical leader, Golden Brain.