At the end of a classified presentation by the SecNav, a security system detects a bug, which proves to be inside a pen on the person of the SecNav, who tells Gibbs that she attended three classified briefings yesterday. Tony contacts the National Security Agency (NSA), where he finds a two-year-old paper describing the possibility of a breach such as the one which just occurred; Gibbs and Tony meet NSA analyst Ellie Bishop, who wrote the playbook. The SecNav receives a demand for money to prevent a leak of classified information; Ellie proposes a plan, and the SecNav approves it. Ellie identifies a suspect, Stalin, and Abby elaborates; Ellie's boss at NSA dies of gunfire; Gibbs, Tony, and Ellie catch Stalin, who provides a name and an address of another suspect; the gang find him and some evidence, Ellie puts the pieces together, then Gibbs and others nail the man responsible. Gibbs tells Ellie that he wants to keep her around on a joint duty assignment.