Stillwell tells Voight he plays by his rules or he goes back to prison. Olinski's daughter Lexi is a witness to a crime. Olinski quickly protects his daughter and doesn't want her to testify. Ruzek brings Burgess into the case that's quickly turning into a gang war.  

Jay goes to Jin about the family he's harassing. As things escalate in the case pressure mounts to get Lexi to testify. Voight and Olinksy decide that they need to get in front of the case to save her from testifying. Jay and Voight have words and Voight informs him he needs to know exactly what he's doing so he can protect him. Jay thinks the son is going to kill another kid. 

Ruzek gets his phone stolen with sexting pictures. He follows the boy who leads him to a stash of cell phones his family sells to the gang to keep food on the table. Following the trail of cell phones the unit goes right to Kulaka. Stillwell calls Voight to show him the body of the man Jay's been harassing.