When an antiterrorism device is stolen, the team must quickly find the suspect and the device before an attack is made against Los Angeles. Meanwhile, Hetty realizes the case is bringing her back to someone from her past.
Psychologist Nate Getz is back in LA, the newest in Deek's line of partners while Kensi is still in Afghanistan. Sam and Callen are taken back to their first case as partners as they search for "TUHON", a suspect in the murder of a diplomat.
The unit teams with an undercover DEA agent to determine whether a bomb blast at an LA fish market was a criminal act or terrorism. In Afghanistan, a helicopter crash give Kenzie and Grainger a lead to the whereabouts of The White Ghost.
When an undercover agent is identified and executed by a local gang, the NCIS: Los Angeles team must locate the mole before other agents' lives are put in danger. Meanwhile, Granger begins to worry when Kensi disappears in Afghanistan.