When a bridesmaid fails to show on the wedding day, mainly because she's, well, dead, it falls to Castle and Beckett to find the murderer. Castle is stunned to find that the bride-to-be is an old flame, Kyra -- "the one that got away" (guest star Alyssa Milano). Complications follow as Kyra, distraught by the event and with the wedding briefly in abeyance as the investigation takes place, begins to question her choices. Beckett rightly doubts if Castle can be objective about the case and Kyra's place as a suspect, but when it looks to Beckett like Castle and Kyra might rekindle their romance, her own objectivity may be just as compromised .