A major security breach in the city’s computer networks forces Firehouse 51’s senior leaders to take matters into their own hands.

Severide gears up for an arson investigation.

Air Date: Wednesday, Oct. 27 (09:00PM – 10:00PM) on NBC.

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CHICAGO FIRE -- "Dead Zone" Episode 1006 -- Pictured: (l-r) Taylor Kinney as Kelly Severide, Andy Allo as Seager -- (Photo by: Adrian S. Burrows Sr./NBC)