At a research facility of the US Department of Energy in Los Angeles, an intruder steals electronic data and leaves, then a third thug shoots the thief and his wheelman, then a security guard intervenes, and the third bad guy shoots the guard while the wheelman escapes, leaving the thief and the guard on the pavement and taking the stolen data; the guard was a retired Marine gunnery sergeant; the data pertains to an antiterrorism nuclear-detection system. G and Sam visit the home of the wheelman, whom they find dead; G and Sam visit the injured guard; Nell does a chore for Hetty, Eric provides data, and Hetty serves as backup; the foursome respond to an alarm and find a person of interest but no bomb or other hot material; Nell sees a special person, G and Sam grab him, and Hetty chats him up at the boatshed; the foursome, with Nell's help, pull a scam on a bunch of Russkis, recover the data, then move out; Granger freaks out, but everything works out.

Sam insists Callen find a new partner while a threat of a North Korean attack looms.