Andy tells everyone that she called things off with Luke because things were going too fast and they both need some space. Sam doesn't buy it. They respond to a break-in call at an apartment. They only find that underwear is missing from Sophie's apartment and Andy decides to wait until Sophie finds a place to stay before leaving. Shortly after she leaves, Sophie is attacked. She was strangled until she was unconscious and her body was bound with duct tape. The state in which she was found coupled with the missing underwear bears a resemblance to one of Luke's unsolved cases. These crimes had been attached to a killer who had got one of 15 Division's rookies, Zoe Martinelli.
Ray Nixon, an army sergeant, is the primary suspect in this case. One of Sophie's neighbors is able to pick Nixon out of a lineup, telling Luke he saw him in the alley. They search Nixon's apartment which yields nothing, and he also had an alibi. After Luke catches Nixon eyeing Andy he threatens him up against the car and is forced to turn to turn the case over to Jo.
Andy is less than thrilled to be working with Jo after what happened with Luke. Things get worse when she goes off to pick up pizza. She challenged Jo's opinion that the case is not related to Martinelli. Sam, after witnessing the heated argument between Andy and Jo, started to figure out what really happened between the two. Luke tells Andy that he is positive that Nixon is the killer. They also learn that his alibi lied. Nixon was actually sleeping with the girl he said he was having a beer with during the attack. He believes that like many killers, Nixon might have mementos from each victim somewhere and decides to start checking out storage facilities in the area. Sam is frustrated that this investigation is going nowhere. He's also bothered by the fact that Andy has so much faith in Luke's theories even after he cheated on her.
The police find green fiber on the duct tape binding Sophie. Dov and Gail recalled seeing a green shag rug in the neighbor's apartment. When they go back to search the place they discover that he's already sterilized the apartment. They find the carpet in the trash and the neighbor is arrested for the attempted murder.
Andy heads to the storage unit and starts looking around in a unit that was listed with the name Zoe Martinelli. After sifting through the items in the unit she finds the mementoes that Luke had been talking about and she calls him in order to get the warrant out for Nixon's arrest. Ray Nixon appears out of nowhere and binds Andy with duct tape. Right as he begins to strangle Andy, Luke appears at the unit and rescues Andy. Luke appreciates the fact that Andy is the only one who backed him up on his theory and he wants her back. He wants Jo out of his life.