Local cops, acting on a tip, find the body of Marine Pfc. Riggs, who was UA; Gibbs and company investigate; Palmer finds two marks on Riggs's neck. Meanwhile on a public street three grim-faced Hoovers demand that Abby go with them; a suit delivers her to Jones, an official at a well funded lab at a hospital for work in a clandestine and highly classified program. While checking out Riggs's car, Gibbs and Ziva find evidence suggesting that he was not an intended victim but rather a bad guy. Gibbs realizes that Abby has taken the place of Heller, the man who was Riggs's target; McGee and Ziva find Heller, who gives explanations. A patient disappears, and a nurse dies. Tony finds Abby; he and Ziva return her to the office. The gang start putting the pieces together; Jones disappears, but they catch him. Gibbs and Jones have a chat, and Abby helps Gibbs with his interrogation. The team finish putting the pieces together, then they tie up the loose ends.