Operation: F.O.U.N.T.A.I.N.

The DCFDTL kidnap the team's classmate, a nerdy, spit-talking girl named 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 Leaky-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.

Una niña fea llamada Leona es raptada por los de la otra cuadra. Número 5 y sus amigos tienen que rescatarla, antes que los de la otra cuadra hagan con ella algo que 5 no podría perdonarse, para lo cual, atraviesan peligrosos obstáculos hasta dar con lo que parece ser la «Fuente de la Juventud.