Enemy on the Hill

A contract killer who has evaded arrest over a lengthy period of time flees a news camera crew, but lapses into a coma when struck by a passing van, eventually dying from his injuries. Evidence found on the assassin's body identify his next victim as Navy Lieutenant Commander Geoffrey Brett, a naval officer working as a legislative aide on Capitol Hill. Gibbs and his team act as Brett's protection detail while, sifting through his finances, the team find millions of dollars that have been stolen from the Navy in an account established under the name "George Kaplan".

It is revealed that Kaplan's money manager, Drew Turner, is paying off her gambling debts by embezzling from Kaplan, and was also responsible for hiring the assassin. When Brett hears Kaplan's name, he eludes Ziva in order to find Turner, who is later found hanged in an apparent suicide. Ducky establishes that Turner was in fact manually strangled before being hanged. At the same time, Tony, a film aficionado, remembers that "George Kaplan" was a phony identity created in the 1950s movie North by Northwest. In a final interrogation scene, Brett confesses to accepting large kickbacks from defense contractors in exchange for his influence on Capitol Hill, but insists he was accumulating the money for his daughter's medical care, not for himself. Turner helped him launder the proceeds with the false identity, but when he learned she had embezzled from him and was trying to have him killed, he killed her first.

In a subplot, after volunteering to donate a kidney, Abby discovers that she and another potential donor are a DNA match, and that the other donor is her biological brother. This revelation leaves Abby stunned and so distracted by the thought of her parents giving a child up for adoption that she can't focus on the case, even forgetting to do the simple things like running evidence. After she is told by the hospital that they can't release her brother's name, Gibbs and McGee find it out themselves. Abby meets her brother, Kyle Davis, but doesn't tell him who she is. On a hunch, Abby compares her DNA to a lock of her mother's hair, which she keeps in a locket, and is shaken to learn that she herself was adopted, and her mother and father are not her biological parents. This revelation leaves her distraught and turning to Gibbs for comfort as she begins to wonder why her birth parents gave her up.