The episode begins with a radio message with the cops reporting two fleeing suspects; they call for back up. They chase the suspects to an alley, exit their car, and continue chasing them on foot. The report after they get out of the car is not clear. There are noises coming from the alley, and there is a gunshot.
A huge crowd of protesters has gathered in front of the Police Department. The victim is Timothy Brown and he was involved in a jewelry store robbery. A high ranking police officer has stated that Timothy had a gun, but others are saying that he was unarmed at the time of the shooting. The other victim was unarmed as well.
Officer Kevin Hopkins is being interrogated by Don and Mac. He tells them that the kid had a gun and he shot him. He is astounded by the fact that his word is being questioned. Mac wants to know the whole story. Kevin tells them that he and his partner, Trey, got separated in the alley. He followed Timothy. Timothy ran around a building and Kevin pulled out his gun. Timothy fired a shot at Kevin. Kevin reported that he was shot at. Mac tells him that there is no such code reported. Kevin continues to tell them that he came out from behind the building and saw Timothy’s hand in one of his pockets, so he fired. Trey arrived and Kevin told him that he was shot at. However, they did not find any gun on Timothy. Don and Mac are not too convinced.
The mob outside gets violent and they barge into the precinct. There is chaos and a number of police officers and civilians are injured. They interrogate Trey, who tells them that the suspect he was following threw his jacket on the fence and ran off. Trey lost him. The generator in the alley was too loud. He went to back up Kevin and heard a gunshot. He saw that Timothy was lying dead on the floor with some jewelry falling out of his jacket. Don is not sure whether Trey is lying. He tells Jamie that Trey could have easily saved his partner by saying that there were two shots that he heard; but he didn’t. He wonders why. Meanwhile, the team gathers evidence from the alley. Timothy’s girlfriend, Tori, tells the press that Timothy was not a violent person and he would never rob a jewelry store.
There are now 1500 people outside the building and Mac is worried. Jo does not find any gun in the alley. Sid calls Mac and tells him that there is no gunshot residue on Timothy’s hand. Mac confronts Kevin, who tells him that he can go to his grave swearing by what he told them. Kevin tells him that he could prove his statement if they take him to the site. That would be too dangerous, so Mac decides to bring the site to him. Hawkes and Adam go to the crime scene with a video camera while Mac and Kevin look at the screen. Kevin tells them the spot where he was shot. Hawkes finds an impact mark and, further down the alley, he also finds a bullet casing. So, it seems Kevin wasn’t lying.
The team decides they need to get Kevin and Trey out of the precinct. They try to hide them in an ambulance and take them out, but the mob manages to pull Kevin from the ambulance. They drag him through the crowd. Mac and his team arrive and manage to rescue Kevin. Hawkes finds a lead on the casing and tells Jo that these casings are an exact match to the ones that were involved in previous shootings from the same alley, but no arrests were made. Danny finds a piece of paper in the jacket of the perpetrator, who threw it on the fence. That paper is a summons. They figure out the gang’s common hangout area, but they still don’t know who they are looking for. Mac tells Jo that Trey’s ambulance got away unharmed and Trey had got a look at the perpetrators. They could search the neighborhood and he could identify the men.
Adam arrives with some new information. He tells Mac that he did some digging around and the jewelry found in Timothy’s jacket belonged to him. He was trying to pawn it to get some extra money for an engagement ring. Adam tells Mac that he went to the store where Timothy bought the ring, and the owner told Adam that Timothy was at his shop when the robbery took place. This means that Timothy was not involved in the robbery.
Jo, Danny, Lindsay, and Trey are driving around the neighborhood, hoping to locate the guys that Kevin and Trey were chasing. They find them. The guy Kevin was chasing is caught but the one Trey was chasing runs off and tries to grab something from a mailbox. Jo shoots him. Lindsay finds a gun in the mailbox. Lindsay and Danny interrogate Griffin, the guy they arrested. He tells them that the gun in the mailbox belonged to everybody. He tells them that they didn’t mean to use the gun, they only wanted it to wave it in front of people who tried to act tough. He tells him that he didn’t mean to kill Kevin, he only wanted to shoot at him. He says that after firing the shot, he ran and hid in one of the buildings in the alley and Timothy just walked by. So, it appears that Kevin mistook Timothy for Griffin because they were wearing the same jacket. Tori is called to the precinct and Mac tells her what happened. He tells her that Kevin did not know that he was shooting the wrong guy and now he is going to have to live with it for the rest of his life. He then gives her the engagement ring that Timothy was going to give her. Tori is in tears. She does not take the ring and walks out. She then makes her statement to the press. She tells them that it is not entirely Kevin’s fault; she also blames the real criminals. Tori says that she might find a way to forgive Kevin, but she will never forgive the two men who took away the most precious thing in her life.
The mob has dispersed. The whole team is on the roof, enjoying a drink, but Mac isn’t with them. He is waiting for Christine in front of her house. Christine arrives and he tells Christine that he doesn’t have a ring or a speech ready but he also doesn’t want to waste another moment waiting. He asks Christine to marry him and she says yes. The episode ends.