After NCIS fails to locate a mole in the department, Under Secretary of Defense Corbin Duggan insists on new leadership and takes over the Los Angeles unit from Hetty and Granger. Also, the team travels to Syria to apprehend a High Value Target where one team member is severely injured when the mission goes awry.

After a Homeland Security agent is poisoned by a notorious Triad assassin, NCIS uncovers a warehouse of counterfeit purses and a money trail to stolen government funds. Also, Nell joins the team in the field.