An old colleague of Gibbs's asks for help.
The NCIS team races against time to thwart a terrorist plot to unleash a dirty bomb on DC. However, matters are complicated when Gibbs’s nemesis Margaret Allison Hart resurfaces to defend one of the prime suspects.
The team is first on the scene when marine Roman Vega is killed after his car explodes during a high speed police chase. The source of the explosion seems to be the trunk of the vehicle, but Ziva concludes that the lack of detonator indicates that it was an accident. However, when McGee notices that he has no signal on his mobile phone, he begins to suspect that the bomb was radioactive – and a scan with a Geiger counter confirms his theory. After they have had a spell in a mobile decontamination unit, Abby arrives and informs her relieved colleagues that they were only exposed to a low dose of radiation.
However, Roman’s vehicle was used to transport cobalt-60, which is a by-product of nuclear reactions and often used to make dirty bombs. “If it could be used to make a dirty bomb, the important question is, where is it now?” Ziva asks. As the team sets off to learn more about Roman’s possible terrorist connections, a man named Walter Kane arrives at NCIS HQ. Kane runs a private intelligence firm that works for the Pentagon, and he is sure that Roman was working for a Peruvian terrorist cell known as Libertad Neuva. Meanwhile, Roman’s brother Alfonso is brought in for questioning after he is found hiding out in a hotel. However, Gibbs is astonished to find that his lawyer is none other than M Allison Hart.
Back at HQ, Hart reacts with customary spikiness when Gibbs attempts to question her client.
However, Alfonso is keen to know more about his brother’s fate, which leads him to clash with his attorney. “I want answers too,” he snaps. It quickly becomes apparent that Roman was hiding a dark secret. “I don’t know what Roman was mixed up in,” Alfonso claims. “But whatever it was, it had him really freaked out.” He provides Gibbs with the address of a Virginia warehouse, which he knows his brother visited frequently. Inside, the team finds a factory equipped with all the components to make a dirty bomb – and a video recording of Roman threatening to unleash it on the city.
Gibbs and his team are relieved that Roman is no longer alive to carry out his threat, but this turns
to panic when Ducky appears with some devastating news. An autopsy has revealed that the dead man is not Roman Vega but an ex-army man named John Cook. “The corporal is alive,” Ducky announces, grimly. “He can give whatever orders he wishes, whenever he wishes.” Can the team find Roman and stop his organisation in its tracks, or will Hart continue to stand in the way?