Evidence recovered at a series of fires indicates that Lt. Severide is being targeted by an arsonist. Meanwhile, Battalion Chief Boden clashes with Gail McLeod, a high ranking consultant with the State Marshal's office who keeps a sharp eye on budgets and performance at the city's firehouses -- and has 51 under her microscope as one that could face the prospect of being closed. Elsewhere, Lt. Casey reflects on the year anniversary of Andy's death, Shay has suspicions about Severide's paternity and Mouch enjoys a visit from Mari, his Japanese girlfriend.

Lt. Severide has his strong ideas on who the serial arsonist is, but first needs to find proof to back up his suspicions. Meanwhile, Lt. Casey adjusts to his new lifestyle in the wake of recent events and Molly's bar is failing, much to the dismay of owners Hermann, Dawson and Otis. Elsewhere, Dawson goes out on a date with Jay Halstead, one of the bar regulars, and Mouch's campaign trail starts to get on track with the aid of Isabella, an old friend of Dawson's.