Witten and her partner are frisking a suspect when he decides to run. Unfortunately, they're running up the steps after him and Witten's partner, Leary, has to stop and rest, leaving Witten with no backup. Witten confronts the suspect on her own and he pulls a knife, refusing to drop it until Leary finally shows up.
An out of breath Leary says that everything turned out fine and that Witten shouldn't be mad. Frank views this via body cam footage. Garrett says this footage may be leaked to the press if Frank doesn't toughen up fitness standards, which Sid finds insulting because he is a bigger guy and doesn't want to be seen as unfit.
Frank has to keep stopping arguments between Garett and Sid about this. It soon seems like a moot point, as the union leader rejects the idea of fitness standards on the grounds that it will cause cops to lose their jobs.
Meanwhile, Danny and Maria get a cold case and it turns out Sid was the original detective on the job. Sid is unhappy with Danny investigating the case and Danny considers stopping, but Maria talks him out of it. Danny and Maria go to see Sloane, the top suspect in the case, and get nowhere, but find he doesn't know Sid personally.
Sid returns and admits he was embarrassed that he didn't do his best work on this case and that they were going to solve it easily. He volunteers to help. Danny makes sure Sid sees a paper that lets him figure out that Sloane was giving his witnesses firearms licenses in exchange for alibis, though Danny denies that he did this.
Elsewhere, Anthony develops an attachment to a foster kid who may be an alibi witness for a woman who is accused of killing another foster kid in the home because he was disabled. Erin is concerned about Anthony's emotional investment but Anthony ends up taking the kid in himself and arranging for him to go to the police academy when he grows up.
Finally, Jamie and Eddie have a fight when Jamie discourages Eddie from joining Witten's all-women softball league on the grounds that fraternal organizations are bad news and that Witten likely wants to use Eddie for something or other.