A Russian operative with valuable intelligence disappears after his Navy escort is killed when the SUV they are riding in gets run off the road. Gregorio and Percy are moving into their new apartment. FBI Director Isler and Special Agent Barnes are in New Orleans looking for the missing operative. That's because the operative, Alexander Petrov, has a complete list of Russian operatives in the U.S. Alexander calls Eva Azarova, a former Russian sleeper agent. Pride and Isler visit Eva in prison. She says she's retired. Eva says she'll help them find Alexander, but Pride walks away until Isler intervenes. Gregorio and Eva, who had previously had a fling, team up. They find Alexander at a Russian safe house. Two assassins break in on them, and Eva and Gregorio prevail, but Alexander escapes. Pride interrogates the female operative, who warns him not to trust Eva. Pride lets Gregorio talk to Eva. Eva admits that Alexander is her brother. Patton and Sebastian crack the operative's cell phone and discover there's another hit squad. Percy goes to let Gregorio and Eva know, but they've disappeared. Sebastian discovered that Gregorio called Pride before she shut off her phone. Gregorio and Eva find Alexander at an amusement park. Alexander saw Eva's name crossed out on the operatives' list, so that's why he came to America: to warn her. Barnes bugged all of NCIS's technology. She shot Eva, then turned to Alexander. Gregorio tackled her, and LaSalle and Percy took out the assassin chasing Alexander. Gregorio bested Barnes. Isler fears the fallout for his career from this public shootout involving a sleeper agent. A cadaver is taking Eva's place, as she goes into witness protection.