In the Middle East, a prisoner, Yusuf, is brought before an American soldier, Daniels. The prisoner insists that he only delivers fruits and vegetables, but the soldier warns that they know he's with Al –Qaeda and demands to know where missing explosives can be found. When Yusuf says nothing, Daniels says that if he says nothing then he'll have to talk to his boss. When the prisoner still doesn't respond, Daniels calls in his boss: Carter.
A man says that she's getting too close and has to go, today.
At the precinct house, Carter meets with Mrs. Kovach, who is there to bail out her abusive husband. Carter talks to her privately and tries to convince Mrs. Kovach that her husband will eventually beat her to death and claim she was accident-prone. Mrs. Kovach insists that she fell down the stairs and Carter tells her to call if her husband hits her again. Mr. Kovach is released and Fusco warns Carter that she can't save everyone. He also has a report on the DNA of the person who shot at her, and that half of it matches Marlene Elias and the other half matches Don Moretti.
Carter goes to see Moretti in prison and accuses him of murdering his mistress after fathering a son, Carl. Moretti denies it but Carter says that his son has grown up and is killing cops and crooks alike. The don points out that he is in prison, but Carter warns that Carl will come after him eventually. She offers him protective custody if he helps because Carl is too well connected, but Moretti points out that Carter hasn't been able to do anything about Carl. Disgusted, Carter starts to leave and Moretti points out that it looks like she's all alone and that Carl will come after her.
That night, the police respond to a murder of a boy gunned down in the street. Fusco and Carter arrive and she confirms that the boy is Ronnie Middleton, who witnessed a shooting six months ago and ID'd the killer, Hector Alvarez. Ronnie was frightened into recanting his testimony, but Hector killed him anyway. They find a bottle of Mexican soda on Ronnie's body and Carter spots a local bodega owner. She tells Fusco to talk to the locals while she talks to the owner, Castillo. As Fusco canvasses the witnesses, he spots Reese in the crowd. Reese wants to know what happened
Carter talks to Castillo, who claims he was busy in the back and didn't see anything. She doesn't believe him and points out that Ronnie bought the soda at Castillo's bodega. The owner tells Carter that he can't talk there but will come down to the station to tell her what he saw. As Carter leaves, Reese watches her and gets a call from Finch. He tells Finch that Ronnie is already dead, but Finch tells him that the new number that came up is for Detective Carter.
The next day, Carter meets with her son Taylor and wants to know where he was. She tells him to stay with his grandmother until Carter is done with her current case, and then discusses the upcoming dance at his school. Meanwhile, Reese listens from the next booth and force-pairs Carter's cell phone. Finch is planting a tracker and camera in her car and manages to get out just as Carter comes out. Reese continues to follow her as she goes to Hector's car shop. He insists that he was with his girlfriend Monica watching TV, and Carter warns Hector that killing Ronnie was a mistake and she'll run him down.
Finch is planting a camera in a police officer bobblehead doll when Reese comes in. He explains that the doll is a "gift" for Fusco to put on his desk so they can monitor Carter. Finch then goes over Carter's record, including the fact that she served as an Army interrogator. They figure she's made a lot of enemies, over 300, and Finch suggests that Kovach, Hector, and Elias are all likely suspects. Reese insists on watching her despite the risks.
At the station, Fusco gets the doll and Reese calls to explain that it contains a camera. Fusco wants to know if Carter is in trouble, and Reese tells him to check with his corrupt pals. Carter arrives and tells Fusco that Moretti shut her out, and asks about Castillo. The owner hasn't come in and Carter goes to get him. Fusco tells her that he has other business and will catch up to him later.
As Carter drives to the bodega, she pulls over and arrests a suspect. Reese, following on motorcycle, figures something is wrong. However, it's a ruse so that Carter can talk to her snitch, Bottle Cap. She asks him about Elias and Bottle Cap admits that he hasn't heard much. He also doesn't know anything about Ronnie's murder or heard anything about Hector. Carter pays him off and tells him that there's more where that came from if he can come up with info on Elias.
Fusco meets with his former captain, Lynch, and explains that he's starting to hear rumors that people in the department want to eliminate Carter. Lynch says that Elias knows the rules and has things under control, with contacts all the way up to city hall. He admits that Carter is gunning for Elias and has to go, and that he's received permission from his superiors to eliminate her in the line of duty. Fusco is uncomfortable with being stuck in the middle and Lynch tells him to keep his distance.
Carter finds Castillo at the bodega and he explains that he learned that Ronnie was a witness. He doesn't want to testify, but Carter warns that Hector will kill him on general principles. Meanwhile, Reese contacts Fusco, who warns that his superiors plan to eliminate Carter and that any case she checks out could have someone waiting for her. Meanwhile, Castillo finally admits that he saw Hector in his store, but refuses to give her a statement. Carter leaves and finds Hector outside. He pulls over and warns her that she should be careful on the block. Hector asks if she has any kids, and Carter tells him that if she sees him again, she'll impound his car. The mechanic says that he'll see Castillo around and makes a shooting gesture at Castillo, who is watching from his bodega.
Reese figures that Elias will use a suspect in one of her cases to eliminate her. He then follows Carter to a bar where she has tracked down Kovach. Kovach insists that what happens between him and his wife is none of her business, but Carter says that she'll come after him if he beats his wife again. He threatens to shoot her but Carter refuses to back down. After she leaves, Reese figures that Elias will hire Kovach.
Carter confronts Yusuf with the photos of the men he helped kill by supplying explosives for suicide vests. However, he insists that he only delivers vegetables. Carter claims she has photos proving his guilt, but Yusuf says that if he talks then the terrorists will kill his wife and son.
The next day, Carter is at the station looking at photos from Ronnie's camera. She admits to Fusco that she has nothing on Hector, and the security cameras around the bodega don't show Hector's car. Carter figures that since Hector lives 25 blocks away from the bodega, he must have had a mistress. They figure that Hector was on foot after coming from his mistress', and that they can get her to place Hector near the crime scene. Fusco gets a call from Reese and takes it privately. Reese tells him to follow Carter and keep her out of trouble while he takes care of some other business. When Fusco wonders why Reese is so concerned, Reese says that Carter is a good person. The detective suggests that if Carter were killed, things would be easier for Reese, and Reese warns him that if anything happens to Carter, he'll come after Fusco next.
Reese goes to Hector's car shop while he's out and blasts open the door with a grenade launcher. He then shoots down Hector's men and finds the guns that their boss is running. Reese collects them and drives away in one of Hector's cars.
Carter promises to protect Yusuf and his family if he helps her. He points out that she doesn't care about him and his family and it's just a negotiation. Carter knows about his son, who can't play soccer because the field is too dangerous, and his brother who was killed by an IED. She insists that Yusuf is not just a negotiation to her, and he asks if she has children. Carter says that she has one and Yusuf asks if she would trust him to a complete stranger. Carter says that they've both lost people close to them and want the same thing: their children to be able to walk safely down the street. Yusuf finally offers to take her to the location of the explosives... for their children.
Carter and Fusco go to see Bottle Cap and ask if he's found out anything about Hector's mistress. Bottle Cap confirms that Hector is stepping out with Mei Li, a stripper. Carter promises to pay him the reward money later if his tip pays off, and Bottle Cap, agrees, saying that Carter is his favorite cop.
Next, Carter calls in Monica and lets her know that Hector is cheating on her. Monica doesn't believe it, but Carter has Hector's cell phone record, complete with 39 calls to Mei Li. They dial the number and confirm that the phone belongs to Mei Li, who is in the interrogation room with Fusco. They put the two women in the interrogation room to settle their differences. Officer Valentino informs Carter that they have a report that someone shot up Hector's car shop. She figures that it's her mystery man, and then learns that Hector has gone missing.
Finch is watching Carter on the camera as Reese comes in and tells him that he's eliminated Hector as a problem. Finch warns that Carter will track down Hector to get justice for Ronnie. Reese figures that Hector will be well armed and that he has to find him before Carter does. When Finch asks if anything is wrong, Reese says that Carter has been doing what they've been doing her entire life, and that they can't afford to lose her.
Carter and Fusco check with the two women, who are angry at Hector for playing them both. Mei Li tells the detectives that Hector went out around midnight and came back from the bodega and changed his shirt. She offers Carter the shirt while Monica tells them that Hector has a warehouse in Queens where he receives shipments. Carter goes to get a warrant but receives a call from Mrs. Kovach, saying that her husband has a gun. The detective tells Mrs. Kovach that she'll be there and leaves. Finch, monitoring her phone, tries to contact Reese without success.
Carter and Fusco go to the Kovach home and find Kovach strung up from the ceiling. They figure that Reese was responsible, and Carter finds Mrs. Kovach hiding in the bathroom. She explains that a man showed up and protected her from her husband. The phone rings and Reese tells Carter that she's in trouble. She warns that sooner or later an innocent person will get hurt because of him, but Reese focuses on her and tells Carter that someone wants her dead. He tells her to be more careful and warns that Hector has an arsenal available. When Carter wonders why he keeps helping her, Reese only says that he always seems to know and drives away.
At the station, Elias poses as a deliveryman and delivers flowers to Carter's desk. He spots her file on him and looks around as Carter and Fusco bring in Kovach. Carter is happy to tell him that his wife is finally pressing charges against him. When she gets to her desk, Carter discovers the flowers and a condolence card concerning her death. She tosses the flowers in the garbage and nervously looks around.
Carter and Fusco take an ESU team to Hector's warehouse. Reese dons a police uniform and goes in with the rest of the assault team. Carter and Fusco are waiting outside and Carter and spots Hector trying to escape. She opens fire and hits Hector, who crashes his truck. Carter arrests him while Reese watches. He then follows her home and checks in with Finch. Finch warns Reese that he's not sure if they've saved Carter. Reese realizes that she's in the wrong part of town and then loses her, and has Finch track her phone.
Carter meets with Bottle Cap and gives him a down payment on his reward. He apologizes and says he has no choice, and then draws a gun and shoots her. As Bottle Cap prepares to finish her off, Reese arrives and kills him.
Daniels and his men report back to Carter and confirm that they took out the explosives. When she wonders where Yusuf is, Daniel tells her that he had an "accident." Disgusted, Carter asks them if they care that Yusuf had a family, and Daniels tells her that it isn't his job to care. He tells her that he and his men won't back her up and she's all alone.
Carter removes her bulletproof vest that Reese told her to wear. He admits that he figures she'll still keep coming after him, but assures her that she's not alone. He calls her by her first name, Joss, and goes. As he leaves, Reese tells Finch that it's time to end things once and for all.
Reese tracks down Lynch and tells him to inform his superiors that Carter is off limits. If Elias comes after her, Reese will put them and Lynch into the ground.
Later, Carter meets with Taylor and asks how his date went. She apologizes for missing it and Taylor suggest that she should quit because he doesn't like her out there in the line of fire. Meanwhile, Finch removes his camera from her car and finds a photo of her dead husband, a soldier. Inside, Taylor asks his mother who has her back, and she tells him that they have each other and don't need anyone else. Reese drives away on his motorcycle and Carter catches a glimpse of him.