Hanna Lowell (Mariette Hartley) is the villainess from "SWAK," the penultimate episode of NCIS' second season (airdate May 10, 2005). She is a former activist who later became the CEO of Lowell Pharmaceuticals.
However, after the rape case involving her daughter, Sarah, went cold with no arrests, Hanna went off the deep end and sought revenge on NCIS, feeling that they lied to protect a midshipman she believed raped Sarah. Hanna sent a "SWAK" letter consisting of a deadly microbe known as Y. pestis, which is Latin for "plague," causing all of NCIS to be quarantined and infecting DiNozzo.
At her office, the villainous Hanna demanded to Gibbs that NCIS admit their cover-up or they will not get the antidote for the plague. She also revealed that she is dying rapidly from an inoperable brain tumor, stating that her chances of seeing her sentencing are slim. Hanna is arrested anyway, and when she learns about someone being infected, she snarled that she hoped it was Westmoreland, who she suspected of raping Sarah. Sarah later admitted that she wasn't raped, and she made it up to avoid family embarrassment.