The case involving Arkady and his personal connection to an oil tanker now leads Callen, Sam, Deeks and Kensi to Moscow, where they must assume many undercover identities to locate their suspect. Meanwhile, Callen uncovers new information about his dad.
DEA agent Talia Del Campo turns to the NCIs team for help after her partner is murdered. Also, after Kensi grows suspicious that Deeks is hiding something, he surprises her by introducing her to his mother.
The team investigates a 20-year-old Peruvian massacre after a well-known fashion model, believed to be one of the survivors, is now a potential target. Also, Kensi goes undercover as the model's assistant and Deeks as her chauffeur.
Accused of sexual misconduct by a former paramedic candidate, Severide faces potentially dire consequences and fights for his survival both within the fire house and the legal system. Voight returns looking to collect a favour from Dawson.
Severide battles the sexual misconduct accusations of a former paramedic candidate. Meanwhile, Casey begins to find satisfaction in his personal life, while Mills and Dawson face challenges in moving their relationship forward.
When a call comes in from the Cook County jail, the squad steps into a volatile predicament and are tasked with trying to defuse an escalating situation. Shay remains hopeful about her baby dreams while Cindy goes into labour.
Evidence recovered at a series of fires indicates that Lt. Severide is being targeted by an arsonist. Meanwhile, Chief Boden clashes with a high ranking consultant with the State Marshal's office who keeps a sharp eye on budgets and performance.
Severide has a strong idea who the serial arsonist is, but first needs to find proof in order to back up his suspicions. Casey adjusts to his new lifestyle in the wake of recent events. Molly's bar is failing, much to her owner’s dismay.
Boden's future with Firehouse 51 is on the line and McLeod keeps on him about his past wrongdoings, pushing him towards an early retirement. It becomes clear who the mole in the firehouse is and everyone expresses their feelings towards him.