WARNING: This article contains major spoilers for Chicago P.D. season 7 episode 12. Read at your own risk.
Chicago P.D. season 7 episode 12 aired on Wednesday night on NBC, with the title "The Devil You Know." The episode sees Voight dealing with Darius Walker to take down a rogue group of dirty cops dealing drugs. However, Upton didn't want Voight's plans and enacted her justice.
In Chicago P.D. season 7 episode 12, the intelligence unit tried to bust a drug dealer and Vanessa Rojas goes undercover. But then, Upton called it off at the last minute and revealed to everyone that the dealer was a cop.
Halstead also believed the drugs came from police custody, and another cop might be involved as well. Voight and others realized that the dealers work with Walker, Voight's CI. He's using him on a secret mission, but Upton doesn't trust this person.
Voight revealed to his bosses that Walker was his CI, but the latter was angered about it. It turns out Upton may have been right all the time, so they began suspecting Walker. The intelligence unit came up with another deal; all the dirty cops would be shot to death.
Later on, Voight told Upton that Interim Superintendent Jason Crawford nullified all the cases, termed the dirty cops as heroes, and will release Walker. Upton was furious about the idea and told Voight that Walker was the only winter in the situation.
Chicago P.D. season 7 episode 12 then sees Upton telling Walker's friends that Walker himself was the reason why their friends were killed. Voight was called to a crime scene, where he found Walker brutally killed. His body was displayed with an 8-ball in his mouth and a rat's body hanging over his head.
Voight asked Upton about what happened to Walker, but she told him someone misunderstood her statement. She didn't regret her actions and said she "learned from the best." But, Voight said her actions would eat her alive, and he's worried about then path she's going on.
Earlier this season, Upton's CI has been murdered because he walked in on Walker at the police station. Upton suspected that Walker was the one who killed her CI, but he had an alibi at that time and said he wouldn't want anyone to find out he's a CI for the cops.
What happened to Upton in Chicago P.D. season 7 episode 12 is similar to Sophia Bush's Erin Lindsay. The character was deeply affected by Nadia's death and decided to go on the dark path. But hopefully, Upton could regain herself and would learn Halstead's self-critical nature to understand her actions.
