In the kitchen of an Italian restaurant, Detective Frank Agnew swigs from a bottle of liquor. "I'm not a bad person," he says. "No, but he is," says Detective Joe Geddes. "The man is a disease."
In a flashback, Joe and Detective Brendan McCann barge into the bedroom of Frank's girlfriend, Katia. "I'm sorry," Katia pleads as Brendan roughs her up. Joe tries to restrain Brendan but is pushed aside.
Back in the present, Joe tells Frank that Brendan cut off Katia's head, hands and feet.
Frank and Joe find Brendan drunkenly slumped at one of the resturant's front tables and help him to his feet. "Big day tomorrow, you got my back?" Brendan asks Joe. "I always got your back," Joe replies. Frank and Joe walk Brendan into the kitchen, where they plunge his head into a sink filled with water and drown him.
Frank and Joe drive Brendan's car to the riverfront. After Frank handcuffs Brendan to the steering wheel so his death will look like a suicide, they send the car into the water.
Elsewhere, Damon Callis and his right-hand man Michael wait for Brendan outside a trap house. Damon orders two of his henchmen to find Brendan, then knocks on the trap house door. A dealer named Billy answers, and Damon barges in, demanding to know where the cocaine is. "You know who that belongs to? There are gonna be repercussions," Billy says as Michael gets the coke. "Do you know who I am?" Damon asks, to which Billy replies, "I seen you." Damon shoots Billy dead.
At police headquarters, Joe tells Detective Dani Khalil about Brendan's drunken state the previous night. Two internal affairs officers, Simon Boyd and Curtis Walker, enter the office. They confer with Lt. Charles Dawson, who asks his receptionist to track down Brendan.
Frank and Joe exchange looks as Curtis searches Brendan's desk. Frank then sets Curtis up in an interrogation room, where he pries unsuccessfully for details about the investigation.
In the men's room, Frank accuses Joe of knowing that I.A. was investigating Brendan. "Did you play me?" Frank asks. Joe denies it.
Joe tells Lt. Dawson and Simon that Brendan was drunk the previous night and that he never mentioned I.A.Damon arrives at his bar, The International, where his wife, Maya, is preparing to open. He tells her that Brendan was supposed to make a bust at the trap house, then give him the cocaine.
On the precinct's rooftop, Frank flashes back to memories of Katia. He removes her necklace from his pocket.
In the men's room, Frank hurries into a stall and vomits, then flushes the necklace down the toilet.
Lt. Dawson asks Frank to go to Brendan's house. Simon says he knows Brendan isn't home because he has footage from Brendan's security camera.
As they watch the security camera footage, Frank recaps the previous night for Simon: He drove Brendan home, then waited in the driveway for Joe. Joe then drove up in Brendan's car, left the car keys in Brendan's mailbox, and departed with Frank.
Flashbacks reveal the actual events: Frank parked his SUV in Brendan's driveway and entered Brendan's house, disguising himself as Brendan by donning a hat and trench coat and stumbling to the front door. Joe then arrived in Brendan's car, dropped the keys in the mailbox, got into Frank's SUV on the passenger's side, slid over to the driver's seat, and drove away.
In Lt. Dawson's office, Joe says he no longer wants to be Brendan's partner if he's dirty.
Referring to the footage, Simon points out that Brendan (in actuality, Frank) left his house just two hours after Frank dropped him off. Frank feigns surprise.
Maya meets Alexander Skelos behind The International and hands over an envelope. Damon arrives as Alexander leaves. Maya reassures Damon that the old man didn't enter the bar. Damon reveals that he'd promised to give up Alexander to Brendan but is now worried that Brendan has double-crossed him.
In Lt. Dawson's office, Joe says he'll be guilty by association if Brendan turns out to be dirty.
At The International, Damon learns Brendan never showed up for work. Maya sees Nick Paflas sitting at the end of the bar and asks if he's working. Nick says that he's on army psych disability and that the only thing he's trained for is killing people.
As Frank eavesdrops, Curtis tells Simon that Brendan's hard drive has been erased. Meanwhile Dani learns Brendan's car has been found, with a body inside.
At the riverfront crime scene, Dani says divers saw a body handcuffed to the steering wheel. Joe suggests murder. Simon suggests a possible suicide.
Frank arrives at the riverfront and accuses Joe of wiping Brendan's computer. "You knew he'd give you up because you're as dirty as he is," he says. Dani notices them arguing.
As Brendan's car is hoisted from the water, Joe tells Simon that Brendan mentioned rats the night before: "I can't keep the rats off of me, I would rather drown," he quotes. "How was I supposed to know he was talking about you?"
Frank identifies the body in the car as Brendan's.
Damon joins Michael near the riverfront and looks at the crime scene through binoculars. He sees Brendan's dead body.
An officer finds a second body in the trunk. "I don't know if I can look at this," Frank says, worried it's Katia. Joe says it's an unidentified male without head, hands or feet.
Lt. Dawson pulls Frank aside and asks him to find out whether Joe is corrupt, saying "This is yours. I'm not gonna trust it with anybody else."
Damon hurls his gun into the river.
Alexander stares down two of Damon's henchmen as they enter The International.
Frank walks to the riverfront and stares out at the water.