Jack Patterson, a special agent of the NCIS, dies on a sidewalk in Washington, DC, in an execution-style shooting right after he drops a package into a mailbox. Abby says that Jack was on his way to meet her; soon she receives the carton from Jack, which contains a painting, which Abby finds to be radioactive. Gibbs interviews a man who introduces himself as an agent of the US Department of Homeland Security (DoHS). Abby learns that the slugs in Jack's body match a handgun used in an unsolved murder in Arizona two years ago; Gibbs and Tony go to Arizona and meet the artist. The real agent of the DoHS shows up in the squad bay; McGee alerts Gibbs, who, while on horseback with Tony, soon receives gunfire from a helo, and they return fire and crash the bird. Gibbs and Tony rescue the artist from harm, and they and the rest of the gang finish putting together the pieces of what happened.