Detective Pryma asks for Severide's help on a case involving explosives; Gallo and Carver clash after Gallo improvises on a call; Violet encourages Brett to start dating again.
The team joins forces with FBI Director Isler after a Russian operative with intelligence on sleeper agents disappears. Tammy partners with former sleeper agent Eva Azarova to assist with the disappearance.
In the wake of tragedy, Manfred vows revenge and, with Olivia and Lem's help, he sets out to find answers about the cursed head in Kai's office. Meanwhile, Joe must square off against a former ally to save Chuy, and Fiji spends a night on the town.