This week on NCIS: Los Angeles, after a Navy SEAL impostor is set ablaze, the team obtains new information regarding the whereabouts of the stolen Brachytherapy canister.
That means the race is on to stop a dirty bomb from being in play.
Also, in a surprising development, Hetty tenders her resignation. It's not clear why, or whether she will be gone for good. But Claire Forlani makes her debut Tuesday night.
Check out the official preview for "Impostors" below ...