While Callen and Sam are aboard the USS Allegiance, the ship is placed under quarantine for possible Ebola exposure. Also, Kensi and Deeks investigate the murder of a petty officer who recently departed the USS Allegiance and is linked to the Ebola exposure.

The NCIS team reluctantly aligns with two former criminals from England, Ricky Dorsey and Frankie Bolton, after a powerful arms dealer kidnaps Ricky's daughter in an attempt to obtain a dangerous weapons system.