Formerly Numbuh One
Abigail "Abby" Lincoln (Numbuh 5) became a KND Operative three years before at least the episode "Operation: M.A.U.R.I.C.E.". She was trained by her older sister, Cree (Numbuh 11), and joined her sister, Numbuh 8a and 8b, and Numbuh 9 in Sector V. After Cree traitorously left the KND, Numbuh 5 became the leader of Sector V, until she somehow messed up (according to Operation: I.N.T.E.R.V.I.E.W.S.) and allowed Numbuh 1 to take over.
Numbuh 5 wears a white-striped blue shirt, red cap that was given to her by Cree, and golden hoop earrings. She has long black hair which she keeps in a braid and she wears white shoes.
The most notable person in Numbuh 5's family is Cree (formerly Numbuh 11), her older sister. She seems to be one of the most evil Teen Ninjas probably even greater than Chad. She started out as a normal innocent teen girl but ended up in her second or third appearance as a threat to the KND. Cree gave Numbuh 5 her red cap which explains how she got it (As shown in Operation: M.A.U.R.I.C.E.) which gives much of her history. Numbuh 5 surrendered to Cree in Operation: M.A.U.R.I.C.E after she gave up on trying. The reason was that after Maurice, an old friend was decommissioned and turned out bad and she couldn't help becoming a teen. She later discovered the truth of Maurice in Operation: M.A.U.R.I.C.E as a spy working for KND. Another family member is her dad who gets mixed up when he talks example: "You know the clowns with their cartoon and puppets and the stuff and-etc.". Abby also has an older brother with a couple of kids as said in Operation: D.I.A.P.E.R. The last member in the family is Numbuh 5's mother who speaks with a French accent and sometimes French. Unlike, the other Sector V agents, Numbuh 5's parents have never shown their faces yet. In Operation: I.N.T.E.R.V.I.E.W.S. it is revealed that she marries Numbuh 2.