Still reeling from the death of informant Anna, Voight faces a new threat as he tries to keep the neighborhood clean. New wrinkles develop in the Upton, Halstead and Voight dynamic. The team gets a new chief.

When a convicted murderer hijacks a prison van, the team scrambles to find him and the abducted prison guard before it's too late. Burgess questions Ruzek's motives in a case, creating tension between the two.

The team investigates a string of brutal pharmacy robberies, and Halstead connects with one of the victims about their Army careers. Upton suspects there is more to the story and confides in Voight.

Upton is unwittingly drawn into a deadly betrayal and finds herself in a fight for her life. With minimal leads, Voight and the team scramble to find her before it's too late.

As Richard Beck's timeline for a deadly attack moves up and Samantha panics, Ruzek and the team scramble to get ahead of unprecedented disaster.