In early 1960s New York City, Officer Terry Muldoon runs the Public Morals Division, a plainclothes unit of the NYPD whose job it is to police vice crimes such as gambling and prostitution. Muldoon juggles various situations and struggles to raise his family in the increasingly violent Hell's Kitchen neighborhood.

Muldoon is tasked by his Aunt Kay to find the person behind his uncle, Mr. O's murder. Mr. O's son, Sean O'Bannon, also a Public Morals officer, starts a romance with best friend Duffy's sister, Deirdre. Shea gets a taste of the fun side of working in Plainclothes when Bullman takes him to a private, illegal casino.

Muldoon and Latucci take their wives on a double date, using the perks of the job to have a night on the town. Shea is partnered for the night with O'Bannon, who has some fun at Shea's expense when arresting a couple of hookers. Kane takes the first step in avenging Mr. O's death.

While looking for a killer, Muldoon and Bullman find themselves in the line of fire. Sgt. Mike invites Patton out to visit him to gain traction with the Mr. O investigation. O'Bannon is put to the test when Muldoon includes him in a pursuit.

Muldoon juggles tensions at home with his family, warns Latucci about his relationship with the Moose, while also pursuing the Pattons. Lt. King helps out an old flame and assembles some fellow officers to take care of a situation. Kane and Hopkins have been hiding upstate and plot their revenge. Patton questions his brother's loyalty as tensions rise.

Muldoon must make a final decision about whether Shea should be in Public Morals and puts him to the test. Kane finally returns to Hell's Kitchen, and it is soon a race between Rusty and Kane to get to each other first.

The streets of Hell's Kitchen run red with the blood of the Irish Mafia, as the west side war comes to a head. Muldoon treats Christine to a night on the town, and makes a decision. Duffy gets surprising news from Deirdre. As Bullman's feelings for Fortune intensify, he's forced to make a decision about their relationship.