As Voight makes his way to dinner, he sees a man kicking a car while on the phone. 

He calls the guy out and keeps it moving. At the restaurant, he meets Superintendent Samantha Miller for a drink. She informs him about the progress Chicago is making.

Her son, Darrell, arrives, and Voight realizes it's the man he saw outside. 

On his way home, Voight realizes he's being trailed and confronts the driver who turns out to be Darrell. 

He tells Voight that he owes some bad men $10,000 and asks him to keep this from his mom. 

Voight tells Miller since she's his boss, and she informs him to play this by the books and put Darrell as a CI. 

Voight informs Intelligence that Darrell is going to go undercover to bring down this drug dealer. Atwater isn't pleased that the Superintendent's son is getting special privilege.

Darrell confronts Kent, the man he owes money and asks him for another buy. When Kent opens his closet, he reveals at least half a million worth of product. 

He's not a small-time dealer like Darrell told them. 

Intelligence is upset because now they have to launch a full-on investigation and find Kent's boss. 

Ruzek and Atwater accompany Darrell as buyers looking to score some product. 

Kent informs them that he doesn't have anything and trash talks Darrell. 

When he pulls out a gun, they withdraw as it becomes clear that Kent is going to sell to them. 

They inform Darrell that they have to lie low and rethink a new strategy. 

Ruzek gets a call at 4 AM and hears Darrell on the other line. He rushes into the precinct and calls in for backup as they begin tracking Darrell's phone. 

They ping it just as they hear that Kent and some other man found Darrell's phone and disposed of it. 

Intelligence arrives at the viaduct and finds the phone. Darrell is nowhere to be found. 

They pull video footage and see that Darrell came to the club earlier in the evening. He left with a woman, Kent, and another unidentified man. 

They ID the man as Roy Walden, who also owns the auto body shop where the traffic cameras picked them up at. 

Voight wants to move in and check the shop, but Miller shuts it down because they don't have probable cause. 

Voight stresses that they're running out of time and need to find her son, but she's adamant about doing things by the book. 

They get a call about a woman matching the description of the one seen at the club. 

Halstead and Upton arrive at the blue line station to talk to her. Sasha, who is 14, reveals that Darrell tried to help her. Kent was upset, and Roy took Darrell inside the auto shop. 

She then reveals they left the auto shop and drove to the water. 

Once Intelligence arrives on the scene, they find Darrell's body.

Miller arrives on the scene and is distraught by her son's murder. 

Voight and the team interview Sasha, who explains that Roy was trafficking underage girls at the club. She is able to give them enough details to pinpoint the stash house. 

Upon arrival, they find that the remaining girls have been shot execution-style. 

Voight says that the men must have known they were coming and were tying up loose ends. 

Voight informs Miller that they were too late. She breaks down knowing that she killed her son. 

Voight rallies Intelligence and all of CPD to find Kent and Roy. Each member of Intelligence has their own team as they hit several stash houses. 

All of them turn up empty. Burgess arrives at one of the houses. As she waits for backup in her patrol car, she's ambushed by a man who beats her until she's unconscious. 

The second part of the episode will continue during the season 8 finale.