The episode kicks off with Ruzek and Halstead undercover to nab the Becerra Brothers, Enrique and Hector.
As they're about to make the exchange, an SUV rolls by and opens fire. Ruzek and Halstead duck, but the Latin Players are killed.
Intelligence is able to look at the brothers' text messages and triangulate the incoming texts to Garfield Park, where Ruzek has a trustworthy CI named Tommy.
Ruzek and Burgess arrive at Tommy's place and see that his child's birthday party is being crashed by the police.
Ruzek takes over and asks Tommy for help on a case.
He agrees and informs him that the person Ruzek wants to connect with is Logan Teague. He promises to make the introduction and assures Ruzek that he's clean, but once they meet with Logan, Tommy gets high.
Logan promises to set them up with Keith Monahan, a guy moving in from Indiana.
Voight learns about Tommy's drug usage and tells him to bring him in. When Ruzek tries to scoop Tommy up, his wife, Isabel, informs him that he's not at home.
Ruzek finds him dealing stolen shoes and coming down from a wicked high.
Voight wants to know if Tommy has what it takes to connect them with a smart, violent dealer.
Ruzek still believes in Tommy, but Burgess isn't convinced.
They respond to another murder by Monahan -- this time a dealer and his 22-year-old girlfriend.
Ruzek informs Voight that they have no choice but to put Tommy into play, and Voight agrees.
They meet up with Logan again, who notices that Tommy is "dry" and offers him more product.
When Tommy refuses, Ruzek, who is undercover as Mike, tells Logan to back off, which prompts Logan to point a gun at his head and tell him to smoke up.
At this point, Atwater and Burgess realize that Ruzek has been made, but they wait for his call, which comes when Ruzek takes down Logan.
Voight calls him into his office later to ask what the hell happened. Ruzek says it was self-defense, but Voight informs him someone captured their altercation on video and is referring to it as "police brutality."
He informs him that in this new world order, perception is key.
Ruzek tries to use Logan, who refuses to flip on Monahan because he says it's a "death sentence."
Ruzek promises to look the other way if Logan will allow him to use his phone to set up the deal, which he does.
Burgess confronts Ruzek informing him that if he allows Logan to walk free, he'll come after Tommy in a heartbeat, but Ruzek is convinced that he'll be able to help Tommy by sending him downstate.
He plans to meet Monahan with Tommy, but Burgess informs him that he could barely make it through the meeting.
Ruzek tells her it'll be okay, but when he gets to Tommy's place, he finds him in really bad shape as the withdrawals get the best of him.
Tommy tells him that he needs more drugs if he wants to get through this. Ruzek is hesitant, but eventually agrees and drives him to the buy.
The next day, Tommy and Ruzek arrive at the buy, and when he begins spewing nonsense, everyone thinks that Tommy is geeking out.
Yet, he manages to make the exchange, at which point Intelligence moves in.
Ruzek goes to chase Monahan and has him cornered when Tommy tries to knock him over.
Monahan points his gun at Tommy. When Ruzek tells him to drop the gun or he'll shoot, Monahan questions whether he actually will with all the cameras pointed at him.
Ruzek hesitates, Monahan shoots Tommy in the chest, and Ruzek unloads his weapon into Monahan.
Tommy apologizes as Ruzek tries to keep him awake while they wait for an ambo.
Back at the precinct, Ruzek is beating himself up over his hesitation and informs Voight that he can't trust his instincts anymore.
Voight tells him that they are navigating a complicated new reality, but right it still right and his shot would have been lawful if he took it.