The body of Laura Cambridge is found in a car that was abandoned in an alley. The victim's purse was found ditched in a nearby dumpster. There was money inside, but no cell phone. A run of the license plate reveals that car came from the motor pool at City Hall. The last person to use it happens to be Castle's good friend-Mayor Robert Weldon.
Mayor Weldon doesn't recognize the victim. He says the car was reported stolen from a fundraiser the night of the murder. Weldon also reveals that he's planning to make a run for governor. Castle and Beckett meet the mayor's Chief of Staff, Brian Shay, and his Deputy Assistant, Jordan Norris. Shay assures Beckett that he will do whatever it takes to protect the mayor. Beckett assures Shay that she'll do whatever it takes to catch a killer.
Laura Cambridge was once a literature professor who cut off all ties to her previous life about six months ago. Her landlord saw a tall, Caucasian man with dark hair leaving her place the night she was killed. Her sister says Laura was in trouble because of something that happened at her job. Castle and Beckett are shocked to learn that Laura has spent the last six months working as a phone sex operator.
The Chief Sexecutive Officer at Dial-A-Goddess says Laura was one of her most popular employees. The company's call dispatcher, Sarah, says Laura asked for the contact information of a client, Edgar Navarro. She needed his help to copy some digital recordings. Laura had heard something on a call. Something bad. Someone posing as a gas man steals the hard drive containing all the calls from Laura's workplace. The imposter matches the description of the person seen leaving Laura's apartment.
The reason Laura went off the grid is because she was writing a book about living below the poverty line. Her agent tells Castle and Beckett that Laura recently stumbled upon scandalous story involving a very powerful, prominent New Yorker. Laura was scanning videotape footage of Mayor Weldon. Fiber analysis indicates that the killer may have been wearing a light brown cashmere coat just like the one Weldon was wearing in a clip that also features the murder victim.
Castle convinces Beckett to keep this new information from Captain Gates for the time being. He refuses to believe his friend is a killer even though the mayor is the subject of an investigation alleging he embezzled $2.3 million from his own charity. Beckett has no choice but to bring Captain Gates up to speed. It's an agonizing decision. Beckett knows that if the mayor goes down, the first thing Gates will do is get rid of Castle.
Gates says that they can keep the wolves at bay for awhile if Weldon voluntarily gives up his jacket for testing. That's something the mayor refuses to do. Weldon believes he's being set up as part of a conspiracy that popped up the moment he considered running for governor. Right now he doesn't trust anyone. Not even Castle.
Castle gets a call from the mystery man who first contacted him in "Rise." This shadowy figure had told him that Beckett would remain safe as long as she stayed away from her mother's murder case. Castle meets with the mystery man who says Weldon isn't wrong about his conspiracy theory. He also tells Castle to listen to the evidence. That's what Laura did.
Castle convinces Beckett to meet him at the Dial-A-Goddess offices. The company's dispatcher, Sarah, recognizes the voice of one of Laura's regular callers from a video featuring the mayor. It belongs to his Chief of Staff's Deputy Assistant, Jordan Norris.
Norris confessed to the embezzling scheme to Laura during a drunken purging of guilt. He is about to give up the name of the person pulling the strings. This is the same person who arranged Laura Cambridge's murder. But that information will remain a secret after an attorney storms into the room to stop all questioning. Beckett is frustrated. She wants the people who are controlling Jordan Norris. That information will remain a mystery. For now.
Mayor Weldon confesses to Castle that his dreams of becoming governor and more are all but gone. Powerful others have already decided that. Later, Castle contacts the mystery man once again. This shadowy figure says that if the mayor went down, there would be no one in the precinct to keep Beckett from looking into things she shouldn't. There'd be no one to keep her out of harm's way. That's something Castle will always do.