Firehouse 51 responds to a fire, and Gallo disobeys orders, deciding to go into house to rescue the family after little boy pleads with him.
Casey figures out Gallo defied his orders and calls Gallo out on his behavior at the firehouse.
Gallo apologizes, but Casey still says Gallo's disobedience will be mentioned in the incident report.
Casey expects Boden to be angry, but Boden believes Gallo will live up to potential under Casey’s tutelage.
Boden then reveals Gallo's entire family died in a fire when he was little.
Casey says Gallo needs to tell him the truth, and by the end of the episode, Gallo opens up to Casey about his past.
Severide and Cruz suspect foul play the fire started by an elderly woman turns deadly. The pair go to OFI and share their suspicions.
Their hunch turns out to be correct when Severide discovers the fire was identical to the set up of a previous fire described in detail in a local newspaper, leading Severide to think the man used to the previous fire as a blueprint for murder and arson.
The case is transferred to Chicago Police Department, and Severide goes to confront the family.
The woman then confesses that she started the fire, not her husband, because she wanted her mother's money.
Brett, Kidd, and Foster decide to turn the blue office into a women's only lounge after reading about the idea in a magazine.
Boden agrees, and the trio decorate the office, welcoming the bliss of a testosterone-free zone.
Other female first responders hear about the lounge, and Brett, Kidd, and Foster allow them to use it.
However, the trio aren't happy when they learn the other female first responders have co-opted the lounge and turned their sacred space upside down.
Kidd admits to Boden the idea backfired, and he agrees to shut it down.
Finally, Brett tells the entire firehouse Cruz is engaged, and at the end of the episoe, Cruz asks Severide to be his best man.