NCIS:LA investigates the murder of a man posing as a retired Navy Seal who was hired by a radical anti-government group to make a dirty bomb. The victim, Carl, was posing as his childhood friend and real Navy Seal who died in the Gulf War. He got mixed up with a group of radical anarchists who got their hands on the fourth missing canister of radiopharmaceuticals which was traced to the Yusef Afzal's murder.

The team follows the trace residue of the radioactive material and Nell finds the middleman between Carl and Afzal's killers. It turns out, the leader of the radical group, Shepherd, hired Carl to make a dirty bomb but when Carl didn't deliver on all his fake promises, Shepherd had him killed. Our team sets a trap for Shepherd and retrieves the radiopharmaceutical canister before it is able to detonate.  

Hetty is behaving strangely and as Callen tries to get to the bottom of it, the team finds Hetty is gone and a new Operations Manager has taken her place.