Boden checks the condemned buildings in the area for headquarters, and at one of the building encounters a man with dementia.
The man is taken to Med and keeps uttering the numbers 24198.
Boden looks into it and realizes the numbers correspond to a police badge.
From there, doctors are able to identify the man, and Boden tells the man's wife to call him any time.
The woman later calls Boden, who talks to the man about his dead father, who was also a cop.
Severide accompanies Boden on this and spends most of the episode avoiding Kidd.
Kidd repeatedly asks Severide what's going on, but he is evasive, prompting Kidd to stay with Brett, just as Severide realizes pushing Kidd away won't magically solve their problems.
Casey and Brett both meet potential new love interests at the scene of an accident.
Casey gets along with a car crash victim named Sydney, while Brett hits things off with a fellow firefighter named Greg Granger.
Both, though, are unsure whether they should do next.
Mouch reignites a feud with an old rival, and the pair try to outdo one another with donuts.
Mouch eventually concedes but plans to get revenge later.
Lastly, Gallo says Mackey from being hurt at the site of an explosion.