Dennis Williams Grimes

Atwater reunites with an old friend from his academy days after a bombing rocks downtown Chicago.

Casey (Jesse Spencer) continues his run for alderman, but a citywide propaganda attack against his campaign makes him reconsider his candidacy. The rescue squad is summoned to the scene of a man trapped inside of a burning car with suspicious evidence suggesting that the fire may have been intentionally set. Mouch's (Christian Stolte) upcoming bachelor party looms, but with Trudy's (guest star Amy Morton) nerdy brother Larry (guest star Zack Pearlman) handling the details, everyone fears for the worst. Meanwhile, Jimmy (Steven R. McQueen) and Brett (Kara Killmer) take a kidnapping investigation into their own hands.

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.