Numbuh 14, or Mary-Lou Sarah-Jane Jones, is the leader of Sector N. She was first seen in Operation: M.A.C.A.R.R.O.N.I., alongside her teammates, when Sector V informed them that they have rescued Numbuh 13 and are returning him. To avoid being given the extremely unlucky and troublesome boy, Sector N pretended their treehouse was under attack and then disguised themselves as Mexican fast food workers to stall Sector V's request. Numbuh 14 has also been seen in Operation: H.O.L.I.D.A.Y. and Operation: I.T.. She also appeared in The Grim Adventures of the KND, alongside Numbuh 60, Numbuh 74.239, Numbuh 362, and Numbuh 20,000. She appeared at the very end of Operation: Z.E.R.O., alongside all the KND operatives. She is voiced by Jennifer Hale.
Mary-Lou has puffy, frizzy blonde hair in two pigtails, tied with dark-blue bands, light-blue eyes, and 3 freckles beside each eye. She wears a dark-blue T-shirt with a white stripe going down the middle, white shorts with blue lines around the ends, and huge blue sneakers with white on the sides and bottom. She has tiny white earrings on her ears.
Mary-Lou talks with a Western accent, and presents herself as fairly friendly and inviting. But like the rest of her sector, she is afraid of Numbuh 13, and will do whatever they can to keep him away from their treehouse if he goes missing.