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.