A nuclear explosion reignites the search for stolen weapons; Hetty shuffles partnerships, so Callen and Kensi go overseas, while Deeks and Sam investigate stateside.
When the body of a cartel boss is stolen after a successful special task force mission, the team investigates a potential leak and find the missing remains.
Callen and Sam work with NCIS: Red, a mobile team of agents, when a murder weapon in Idaho matches one used in a national security case in Los Angeles.