Severide and Brittany are out for a morning job. She continues to dodge questions about when he can meet her family.
Cruz asks Brett out for drinks after Zumba. She didn't realize he was asking her out on a date, but she doesn't want to do anything to jeopardize their friendship.
The squad and truck are called onto the scene of a semi-truck that has crashed and is leaking hydrochloric acid all over the road. Dawson reacts quickly and commandeers an excavating truck that's nearby. She uses the dirt from it to contain the leaking acid. Unfortunately, another Chief on the scene points out that she wasn't wearing protective gear, making both Casey and Chief Boden look bad. Casey warns Dawson they will discuss the matter back at the station.
Brittany has showed up at the house once again claiming to miss Severide. She wants him to show her pictures of Shay.
Boden asks Casey about Dawson's misstep, given that it reflects poorly on them all. Boden doesn't want people thinking that Casey is going easy on his "candidate" and offers to talk with her if he's uncomfortable doing so. Casey promises to take care of it.
Casey and Dawson argue about her decision. She tries to tell him that she had to act fast, but he says that following orders is not up for debate. He says if it ever happens again he's going to be forced to kick her off for good.
Mouch is getting his injured eye examined so he can be cleared for duty. The eye doctor misunderstands Mouch's expression of gratitude as a date offer.
Otis confronts Cruz about what's bothering him, because clearly something is. He tells him how he got put in the "friend zone" by Brett.
Brett and Mills respond to a possible drowning victim who at first seems fine, and then starts coding on the way to the hospital. The boy is not able to be saved and dies at the hospital.
It turns out the boy that died is the son of a Chicago mobster, someone known as the "John Gotti of Chicago."
Brett and Mills are upset when they return to the house. Cruz tries to comfort her with some wings and it seems to be working.
Severide takes Brittany to the spot where the Great Fire of Chicago took place, and where he learned all about firefighting. He shares with her how Shay tought him about protecting people, and shows her Shay's badge on the wall. She's grateful that he shared all this with her and in turn reveals to him that she was the one driving the car when her sister was killed.
Mills is confronted by Mr. Lullo, the boy's father, outside of the firehouse and tells Mills that his death is on him. Mills says he tried everything and that he's sorry. Lullo threatens Mills life.
Detective Halstead and Boden advise Mills to stay as far away from Lullo as possible.
Dawson is curious why Casey never showed up at Molly's last night, and she wants to discuss what happened last shift, and she wants to talk fiance to fiancee.
Mouch continues to struggle to cancel his "date" that he accidentally scheduled with his eye doctor.
The squad is called to a store front fire where a man disobeys their orders and runs into the burning building. Dawson and Casey are forced to go in after him. Dawson leaves Casey's side at one point, but they are able to rescue the man.
Brittany tells Severide she has to go home, and he agrees. He tells her that he realizes he's been her escape, and that as long as she's with him her family won't be right.
Trudy shows up at Mouch's date, having found out about it and canceled with Dr. Lu for him.
Brett shows up at Molly's and reconsiders Cruz's offer for a date. She'd like to accept it now.
Severide and Brittany say goodbye as she heads home to Tallahassee, neither of them having any regrets about the marriage.
Mills helps Dawson clean up at Molly's and asks how she's doing, now that they don't talk as much. Dawson says things are going a bit rough with Casey at home and she's not sure what to do. Casey walks in as Mills reaches for Dawson's hand and gets the wrong idea and storms out.