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Lt. Severide is shocked when Rene Royce resurfaces; Casey comes up with a plan to help Chief Boden in his latest pursuit; Kidd regrets a decision she made regarding Severide; Herrmann clashes with Lt. Colannino over their son's basketball team.

With Voight sidelined, Antonio and Ruzek clash as Intelligence races to solve a high-stakes case involving a series of overdose deaths caused by bad heroin.

Intelligence joins forces with Firehouse 51 after a devastating high-rise fire is ruled arson, and Halstead, who has a tragic connection to the fire, struggles to stay objective as he gets deeper into the investigation.

Intelligence's investigation into a string of robberies targeting vulnerable immigrants escalates when a teenage girl connected to a critic of the CPD is kidnapped by the robbers.

Burgess finds herself in a difficult situation when she responds to a call while a civilian is in her car for a ride-along that was requested by Brennan.

Intelligence's investigation of a nightclub owner suspected of cocaine distribution is complicated when Ruzek recognizes someone close to him while working undercover.

When the wife of an alderman is beaten to death, Voight finds himself under pressure from Brennan to close the case; Upton shares a dark episode from her past to elicit a confession.