A bike messenger zooms down the busy street until WHAM! A car sends him flying. The masked driver snatches the satchel from the messenger's lifeless body and speeds away. The package being delivered by the messenger was sent at the behest of an inmate named Brady Thompson. It was to be delivered to the man who put Brady in prison for murder 10 years ago – our very own Captain Roy Montgomery!
The team discovers that Brady Thompson was just killed in prison. Think the murders are connected? Castle does. Brady's wife claims that her husband agreed to take the fall for a murder in exchange for a monthly stipend to pay for their son's medical bills. She doesn't know who the actual killer was, but when the payments stopped coming, Brady told her to go into hiding while he sent Montgomery the proof that he was innocent.
The victim of the decade-old murder was a young woman named Olivia Debiasse, who had attended a family reunion for one New York's most important political families, the Wellesleys. Trent Wellesley is with his grandmother, Lenanne, when Castle and Beckett question him. Their presence agitates the easily-confused Lenanne, and her assistant, Frank, suggests they question Trent elsewhere.
Trent concedes that he argued with Olivia the night of her murder, but claims he was protecting his Uncle Winston from an obvious gold digger. Winston Wellesley tells Castle and Beckett that he had hoped to mentor Olivia, nothing more. Then we're wondering why he paid for Olivia's funeral. Think they were having an affair?
Blake Wellesley, Winston's brother and a candidate for the Senate, says the unannounced police interviews are upsetting his mother and he'd like them to be conducted through his office from now on. Montgomery refuses, sending Blake off in a huff. Don't you just love when haughty rich people are sent off in a huff?
Perlmutter exhumes Olivia's body in an attempt to determine the actual cause of death, but when he opens the coffin, there's nothing but sandbags inside. In a coffin drawer, they find a photo of Olivia's mother when she was working on Winston and Blake's father's Senate campaign as a young woman. Castle finds an article online that says both Blake and Winston worked at the campaign headquarters with Olivia's mother back in '78. He wonders why Winston didn't tell them that. Only one way to find out!
When Beckett and Castle confront Winston with the photo of Olivia's mother, he says that he was Olivia's father. He didn't realize it until Olivia tracked him down after her mother died. We're guessing Winston killed Olivia and disposed of her body to cover up his secret. But Winston alibis out. Hate it when that happens.
As it turns out, Winston claimed paternity of Olivia, but it was really Blake Wellesley who was the unsuspecting daddy. Blake is blindsided by this news. When he confronts Winston as to why he claimed to be Olivia's father, Winston explains that their mother, Lenanne, thought it was the best way to avoid a political scandal.
Lenanne Wellesley admits she wanted Winston to pose as Olivia's father in order to protect Blake from scandal, but says she didn't kill anyone. She only told her assistant, Frank, to take care of it. Frank is about to make his getaway when Montgomery, Esposito and Ryan corner him. Montgomery explains that Frank paid a prison guard to monitor Brady's calls and to arrange for another convict to kill Brady when the time came.
Frank had been doing Lenanne's dirty work for years, cleaning up messes that could hurt the Wellesley reputation. The silver lining is that justice has finally been served for Olivia Debiasse, not to mention Brady Thompson and the bike messenger. Blake Wellesley opts to turn over a new leaf for the family by donating millions of dollars to a local charity that will make sure Brady Thompson's son gets the medical care he needs. Not even Castle could have written a happier ending to this particular case.