The Machine identifies a school teacher who witnessed a mob hit as their next POI. Now, Reese and Finch protect the unfortunate soul who was in the wrong place at the wrong time.
Firehouse 51 is faced with a daunting challenge when an out of control blaze consumes a 15-story apartment complex, trapping victims on the top floors. Complicating the rapidly escalating situation, members soon discover that someone close to home may be one of the trapped victims.
Casey tries to deal with his unsettled personal life and the firehouse welcomes a new member. Boden clashes with new Assistant Deputy Commissioner Jerry Gorsch (guest star Steven Boyer).
Chief Boden becomes increasingly skeptical of Assistant Deputy Commissioner Gorsch's motives, while Severide gets wrapped up in a difficult situation following the rescue of a child from a car wreck.
Halloween is in full effect for Foster and Brett, who are summoned to a home where a prank has quickly turned serious. Gorsch continues his reign of terror on Firehouse 51.