Andy lets Traci know that she and Sam are NOT back together. She's making lists of pros and cons so she can remember why they didn't work as a couple. That's why they are just friends for now. In other relationship news, Chloe is working hard to get back into top form after being shot. She feels she's already there even though everyone else wants her to take it easy. This includes Dov. Chloe wants Nick to investigate the reason as to why he hasn't touched her since she got out of the hospital.
Oliver advises Andy to cut Duncan a little slack in his training. Maybe he'll end up surprising everyone. Duncan is allowed to drive to a crime scene where a body is found in a tenement building's stairwell. The victim, Daryl Riggs, is barely alive. He has a sketchy past. He also doesn't live in the apartment building where he was found. Andy lets the shooting victim's young son know that his father has been hurt. It's a teaching moment for Duncan, who learns that it's sometimes better to act like a friend instead of a cop.
Gail still isn't talking to Holly. She still isn't declaring them as being broken up though. Chris is impressed at how cold she is, but in a good way. While following up a lead on the apartment building shooting, Gail finds another victim bleeding out on a laundry room floor. She tries to keep the woman calm until help arrives. Sam realizes the bullet that wounded the woman came from the apartment upstairs where a dead body is found. The victim is Dominic Cody, head of the Jameson gang.
While Andy talks with Daryl's mother, Duncan tries to glean information from the guy's son by buying him a grape juice. He doesn't get any insight. Andy, on the other hand, learns that Daryl was doing electrical work in the building. This looks like a case of being in the wrong place at the wrong time. Daryl likely saw a member of another gang, the Vipers, during the hit on Cody. Retaliation will be coming. The officers of 15 have one day to find a killer before an all-out gang war breaks out.
There was a bottle of grape juice in Daryl Riggs' car. This leads Andy to believe his son was at the crime scene. That means both father and son were witnesses to the murder. Marcus lets Andy know that they were there when they heard gunshots. He saw the killer. It wasn't a member of the Vipers. It was Cody's number two man, Shay Bishop. The guy killed his boss and was looking to pin it on a rival gang.
Bishop shows up at the house while Andy is inside with Marcus. Duncan is outside in the squad car. A call for backup is made. Duncan is frozen with fear behind the steering wheel. He turns off the radio so he can't hear his partner's calls for help. BANG! BANG! BANG! Andy and Shay exchange fire in an intense gunfight. No one is hit. Backup eventually arrives. Shay Bishop is arrested. Andy and Marcus are safe. Duncan tries to explain that he just got turned around. Andy doesn't buy it. She needed him and he wasn't there for her.Nick awkwardly lets Dov and Chloe know that they both want the same thing. He advises the two of them to get a room somewhere and not tell him anything about it later. In other news, Gail learns that the woman she found in the laundry room didn't make it. She heads back to the apartment complex to find a little girl who is looking for her mom. Gail tearfully realizes what all this means.
Chris has been leading everyone to believe that he's been spending nights with a new lady. In truth, he's making exchanges with a sketchy-looking character in the streets after dark. Also out on the streets are Andy and Sam. Not much is said on their ride home. Sam eventually lets Andy know that her gut instincts about Duncan were right. He believes she's feeling bad about reporting his actions because she believes in people. It's what makes her who she is. This makes Andy feel better. She and Sam share a kiss before saying goodnight and going their separate ways.