The scene opens with Castle getting escorted into a bio-hazard tent. He is put inside a room where Beckett is there as well. Thirty-six hours earlier and a security guard approaches a taxi on blocks. Beckett and Castle arrive on scene and Esposito tells that Admir Alhabi is the victim inside the cab that was stripped. Lannii tells that his fingers were broken one at a time. At the station, Ryan tells that Admir was a cab driver for a while. After Admir shut off his meter, he drove to Washington Heights, a bad neighborhood. Ryan points that Admir wrote down “C41212652”. Beckett visits Admir’s wife, Nazihah. Beckett asks if there was anything strange. She tells that there was nothing. Jamal is Admir’s business owner and cousin and he tells that there are two others who where part of the company too. Kevin McCann and Demitri Verdov were two drivers involved in their business as well. Esposito calls and tells that they have a hit on the car parts of the taxi that Admir was driving.
Beckett and Castle talk to Leland Jones, the guy who sold the car parts to a chop shop. He tells that he stole the parts, but didn’t kill anyone. He tells that there was a guy there at the warehouse around the same time. Castle and Beckett believe Leland’s story. Leland tells that someone was tearing apart the seats of the taxi when he drove up and the guy ran off. Beckett gets a call and it is personal. She tells that she has to get it. Ryan comes up and tells that Demitri Vodolf alibi outs but tells that Kevin McCann was going to be fired. Beckett and Castle talk to Kevin and he tells that Admir was carrying around a lot of money and the fight was because he was not paying Kevin enough. Beckett gets a call from Esposito requesting their presence at the crime scene. They get there and Esposito tells that there were surveillance cameras in Admir’s cab and that the harddrive was torn out of the cab. Things just got more intriguing.
Castle goes home and Martha tells that she is going for a spiritual retreat and tells that she is going to take Alexis with her. Alexis mouths that she has a physics exam and Castle tells that Alexis can’t go because she has to study for a physics exam. Martha tells that she is going to have to go on the retreat by herself. Castle goes to the station to find Beckett having a personal conversation with Josh. Captain Montgomery tells that the cameras were installed by a professional and Ryan pulls up Admir’s financials and sees that $10,000 was deposited into his account. Esposito pulls up Admir’s GPS account and one of his fares drove in a circle. He must have wanted to talk to Admir. Montgomery tells that Techno Pro Systems is the company who installed the cameras. Beckett and Castle go visit the kid who installed them and he tells that Admir had them installed for security.
At the station, Esposito pulls out a picture from the street cameras and it is a man who is carrying a weapon. Beckett and Castle visit Nazihah and she tells that she didn’t know of the $10,000 deposit until it was deposited. She doesn’t know who it could be from. Beckett gets a call with a location of the mystery man. Beckett finds the man and he has a gun, the same type of gun that killed Admir. The man is Fariq Yusef, of the Syrian Consulate. He tells that he doesn’t need to talk to them about anything because he has Diplomatic Immunity and Beckett tells that he can pick up his gun at the station. Fariq is head of security of Secret Police, but is not the killer because he was at a baseball game. Castle realizes that the numbers they found are a location. It is a storage unit and C412 is the unit number. Beckett and Castle get to the storage unit and open it. They open a crate and find and Beckett’s radiation detector goes off and is maxed out. She tells Castle to get out and she calls emergency services and tells that they have been exposed to high levels of radiation.
Castle is escorted into a bio-hazard tent and Beckett is there too. Back at the station, Montgomery tells that they need to keep working on the case and want Ryan and Esposito to dig deep. Agent Mark Fallon of the Department of Homeland Security comes in and tells that he is acting as a liaison. In the bio-hazard tent, Castle asks how bad it is and Beckett tells that her counter maxed out. Fallon talks to Montgomery and barks orders. He tells that it is Montgomery’s case until Ryan tells that Admir was working on weapons in Syria. Fallon tells that he is taking over the case. Castle tells that it was a bomb that was in the storage unit. He changes subjects and asks how Josh is. Beckett tells that he is going out of country again for “Doctors without Borders”. She tells that she wishes that she had someone that she could connect with. A medical team member comes in and says that they found traces of Colbolt-60 that won’t do any harm. Montgomery comes in and tells that a “dirty bomb” was in the storage unit and it is missing.
Castle gets home and Martha tells that she is going to the spiritual retreat without Alexis. Castle tells that he wants her to go with her and Alexis looks at Castle for support. He tells that it will be good for her. At the station, Montgomery tells the seriousness of the case and they have to find it. Fallon tells that Castle can go home and he tells that he is going to stay. Fallon agrees to let him stay. Fallon and Beckett talk to Nazihah and Fallon and Castle tracks the deposit. The deposit was deposited into several accounts before hitting Admir’s, each belonging to a James Smith. In the interrogation room, Fallon talks to Nazihah and tells that they’re going to take her baby away if she doesn’t tell them where the bomb is. Nazihah is hysterical and tells that she doesn’t know anything about a bomb. Beckett is uneasy of Fallon’s tactics and he tells that Nazihah thinks that they believe her and her home is now bugged. Castle sees that they bounced from account to account, but the account originated in Afghanistan. Ryan sees someone entering the storage shed from the recording of the surveillance cameras. It is Jamal, Admir’s cousin.
Fallon briefs everyone of the seriousness of the case and Castle has an idea of what is going on, but tells that he needs Beckett’s help. Ryan tells Fallon that Jamal bought a burner phone. Beckett tells that one of Jamal’s trucks didn’t return. Meanwhile, Castle meets with Fariq in a bar and tells that he needs information about Admir and he tells that he only met with Admir to remind him of his history. Admir left for moral reasons. Admir thought that Fariq was the one who paid him, but he was mistaken. Fariq gives Castle his card. Castle gets back to the station. Fallon tells that he knows that Castle was meeting with Fariq. He asks if Beckett knew about it and Fallon kicks them off the case. At Castle’s home, Castle shows that he took pictures of the board and also has Admir’s driving record. At the station, Esposito shows the van that they are looking for. Jamal’s phone sent a text that tells that the “package has been delivered”. Fallon sets a team to look for the van.
At Castle’s, Beckett tells that a passenger wouldn’t be talking about a terrorist plot. Castle sees that Kevin McCann has been to the same warehouse area. Montgomery gets a location on the truck. Fallon and his team arrive, but there is no bomb. Meanwhile, Castle and Beckett get to the warehouse and go inside. They see a van. They open it and there is a bomb inside with a counter on it set to go off. They get people shooting at them and Beckett tells Castle to go inside a door. He does and the door is locked from the outside. Castle shows that there is a body inside the freezing unit. It is Jamal, Admir’s cousin and business partner and they are trapped inside. The episode ends.