An arsonist firefighter is out to get Station 51, and in the wake of Heather’s accident Casey is forced to step up in a big way with her children. Severide confronts Renee, newly back from her mother’s, about his suspicions of the baby’s due date. She slaps him and walks out of his office, but later at home she admits that the baby is the result of a one-night stand in Europe. She had just convinced herself of a different truth with Casey being the real father.
Elsewhere, Mouch begins his campaign for union president with Hermann by his side. Shay and Dawson feel that they need to get out more, so Shay tries to figure out of her real estate agent is a lesbian and Dawson asks a regular customer at the bar out.