Castle and Beckett investigate an undercover wall street informant's murder, only to run into trouble with the US Attorney, who also happens to be Gates' estranged sister. Meanwhile, the happy couple start work on who to invite to the wedding.
- A Day in the Limelight: Gates this time as focus goes on her and her sister Elizabeth.
- Dirty Cop: The culprit had cocaine planted in Peter's car to frame him for drug possession so she could force him to inform on his boss in exchange for dropping the charges.
- Everyone Has Standards: Elizabeth, normally quick to cite The Needs of the Many, is horrified to learn that her informant was deliberately framed by her assistant.
- He Knows Too Much: After Peter confessed on the wiretap that he was framed for drug possession, Stephanie knew that things would be traced back to her and silenced him before the connection could be made.
- The Needs of the Many: Deconstructed. As it turns out, the drugs Peter was arrested for were planted on orders from Elizabeth's assistant Stephanie all for the purpose of getting the informant they needed. Elizabeth is appalled since justice shouldn't come at the cost of ruining another man's life.
- Title Drop: When the culprit is caught, she tries to justify her actions by saying it was for "The Greater Good".
