The episode begins with a seemingly friendly man noticing a suspicious black car on the other side of the road. He quickly starts walking towards his car. After he gets into his car, he breathes a sigh of relief. At that moment, the man’s car blows up. At home, Castle is playing with his toy car when the phone rings, and the duo gets called to the crime scene. Kate looks at the car and feels that something is not right. Esposito tells her that the CSU had barely started their work when the feds came in and took over.
Kate talks to Agent Garrero from Homeland Security. He tells her that the car is a part of a federal investigation and they are taking the car with them. Pointing out to a black car, Ryan tells the duo that the car was staking out the victim even before his car blew up. Kate and Castle go to talk to the guys in the black car. The two “men in black” don’t answer any of their questions and simply drive away. Esposito arrives and tells Kate that he managed to get an id on the victim, Dale Tanner. Castle has heard about this guy. Kate and Castle talk to Tanner’s wife, Beth. She tells them that after seeing his father being wrongly convicted for murder, helping the under dogs became Tanner’s mission.
Tanner started a website called the “Whistleblower.com” and he exposed a lot of scams through his website. She also tells them that Tanner was about to post some documents online and he was very nervous about it. They ask her about Tanner’s partner, but before she could say anything, Shawn, Tanner’s son, tells the duo that they don’t want to talk about it anymore. At the precinct, Ryan tells Kate and Castle that the feds aren’t revealing any information to them. They aren’t even giving them the name of Tanner’s partner or their financials. Kate decides that they will solve this case without their help. They begin with the bomb in the car.
Esposito arrives and tells them that Tanner’s car was at the garage before it blew up. They conclude that the bomb was planted in the car at the garage. Esposito also tells them that an unfamiliar motorcycle was seen passing by the garage at around 1 am. The security camera managed to get the plates, and it is registered to Monica Lane, and she worked in the security division of the company that Tanner exposed. Monica is shocked to learn that Tanner is dead. She tells them that she was in a relationship with Tanner. Her boss wanted her to get close to Tanner and find out the source. She also tells them that Beth found out about them and had threatened to kill him. Beth is brought in for interrogation.
She tells Kate that she did not kill Tanner, but before she could explain further, Ryan calls Kate out to watch something. He shows them the reconstruction of the explosion, and Kate and Castle are shocked to learn that Dale Tanner was taken out by a drone. Esposito doesn’t believe that it is a drone attack because it is impossible that a drone could fly over New York City. Kate tells him that there is a testing center nearby. Kate and Castle go to the center. There they talk to Officers Fortis and Hooper. Kate and Castle get stonewalled by the word “classified”.
Kate notices a man in the office and remembers seeing him at the crime scene. On their way back, Esposito calls Kate and tells her that the feds came into the precinct and took away all the evidence they had collected. Ryan arrives and tells her that they managed to find Tanner’s partner, Omar Dixon. They also know that Shawn, Tanner’s son,, used to meet Omar regularly. Ryan and Esposito bring in Shawn for interrogation. Shawn gives them a number that his father gave him to get in touch with Omar. Later, Kate meets Omar in the park.
Omar looks nervous. He tells Kate that he was Tanner’s IT guy and he used to only upload the files that Tanner gave him. He also tells her that he doesn’t know anything about the murder. He says that since Tanner’s death, he is being continuously followed. It is seen that the mystery man from the crime scene and the federal office is following Kate and Omar. Kate catches him, but Omar runs away. At the precinct, they learn that the man is Gerard Stack, a private investigator for the Attorney General’s office. He tells them that they don’t have any idea about why the attack happened.
Just then he gets a call from his colleague, who tells them that the drone was one of theirs and someone hacked into it to kill Tanner. Later, Stack arrives and tells them that NSA picked up an encrypted signal the moment the pilot lost control. The hacker did not know how to defeat the signal. They have tracked it down to a location in the lower part of New York. Stack thinks that it could be a guy named, Warburg. He decides to track him down. Kate offers to help, but he tells her that he will take things from here. The team digs around a little to find out about Warburg. It turns out that Warburg thought that the drones will be used against the US citizens and was against it.
To prove that it has already started, he targeted Tanner and framed the government. Kate and Castle manage to locate Warburg. They arrive at a secluded, private property, but Kate has no warrant. Castle decides to walk in as the gate is left open. Moments later, they are attacked by a drone. Kate and Castle shoot it down. Later, Kate finds out that the drone was shooting blanks. Warburg emerges from the bushes and is mad at the duo for obliterating his finest drone. They ask him about Tanner. He admits that he created the software that could hack the drone, but he also says that he did not use it to kill Tanner. He says that he was nowhere near the computer when the murder took place.
He tells them that he wanted Tanner to post his hacking program on his website so that the government is forced to shut down the facility. He says that Tanner refused to post it and sent it back to him. Warburg tells Kate that after he heard about Tanner’s death, he checked the flash drive he sent Tanner. He is sure that somebody copied the program from his flash drive to a USB drive. Kate and Castle now suspect Omar. Stack, who is at the precinct, thanks Kate for helping them locate Warburg. Kate tells him that Warburg did not kill Tanner. She tells him that they have reason to believe that it was Omar. Stack tells her that he can help them locate Omar.
They soon learn that Omar has left the country. Later, Stack and his guys arrive with Omar. He had the Attorney General make some calls and recall the flight back to JFK airport. He tells Kate to question Omar. Omar tells her that he has nothing to do with Tanner’s murder. He admits that he knew about the flash drive because Tanner had sent him to pick it up, and after he decided that he did not want the drive, Tanner sent him to drop the drive at some spot. He says that he has no idea what was on that drive. He also says that the only other person who knew about the drive was Shawn. Later, Kate and Castle go to meet Shawn. They tell him that they know he is the one who copied the hacking program.
They ask him why he killed his father. He tells them that his father never cared for his family. Moreover, he also broke his mother’s heart by dating some other woman. That is why he killed his father. Case Closed. Later, at the precinct, Stack offers Kate a job in DC, where she would report directly to the Attorney General and work on the most challenging cases. He gives her a number and asks her to call and schedule an interview. At home, Kate and Castle have a drink. Castle asks her what Stack wanted to talk to her about. Kate says, “Nothing”. The episode ends.