A man is found suffocated in a car with a plastic bag. The victim is Dr Joshua Leeds, a plastic surgeon. Leeds' fiancée, Courtney Morantz, identifies the body. She's devastated, as they were getting married in a month. She swears Josh was never in contact with any criminal elements.
At Leeds' office, the staff reveals the name of an unsatisfied customer Tracy Goldberg who had sued him, but her alibi checks out.
While Esposito and Ryan search Leeds office for clues, a file is found containing records of an operation with no patient information. It is found that Leeds had operated on a patient for the U.S. Attorney office, doing reconstructive face surgery for a Witness Protection Program.
At the consulate, Candance 'Hard Candy' Robinson refuses to tell Beckett anything about the witness. But Castle, using his sources in the mob learns that Jimmy 'The Rat' Moran was about to testify against a mafia family, the Spolanos.
Beckett meets up with Agent Sorenson and asks him to arrange a meeting with Moran. But the talks are a failure, as the death and nature of death of the doctor scares Moran, who identifies his own killing style being used. After they leave, Beckett is informed that the car containing Moran was shot at and both Sorenson as well as Moran were hit.
Beckett is devastated and blames herself for the hit, but Castle tells her not to give up. Next morning, Beckett tries to find a hole in the staff profiles. They find that Mario, one of the staff members, had just been hired last month. But at the office, it is found that the Maggie Dowd that works in Dr. Leeds' office doesn't match the picture faxed over from her nursing school. They think she may have gone to finish off Moran.
Back at the hospital, Maggie is trying to administer poison to Moran, but gets caught and it is revealed that the line had been cut so that the poison wouldn't enter Moran's line. She is revealed to be Clara 'Cold blood', a hit woman for the Spolanos. She also decides to testify.
There a two subplots to this episode. One concerns Alexis, who is getting ready to go to the junior-senior prom with her friend Owen and Castle's realization that his daughter is growing into a woman.
The other concerns Castle's search for Beckett's mother's killer, which puts a strain on his relationship with Beckett, ultimately leading Beckett to break off from him when he reveals her mother and three other murders at the same time were connected.