S03E06 — Operation: F.O.U.N.T.A.I.N.

The Delightful Children kidnap the team's classmate, nerdy, spit-talking ""Leaky"" Leona, and force her to lead them to the dark underbellies of the school. Alerted by Numbuh 5, the team follows them, and find themselves in an ancient school, laden with deadly booby traps. Avoiding them all, the team finds Leona, strangely aged to an old woman, who leads them to the mythical Fountain of Youth! The KND are amazed at the prospect of remaining ten years old forever, but the Delightful Children desire nothing less than to destroy the Fountain, claiming that the goal of all children should be to grow up. Can the Kids Next door save the supernatural spring? And what strange secret is ""Leaky"" Leona hiding?