Castle - Season 2 Episode 12
A Rose for Everafter

When Castle and Beckett are called to a wedding to investigate the death of a bridesmaid, Castle is stunned to discover that the soon-to-be bride is his old flame, Kyra, "the one that got away". Complications ensue as Kyra, caught off-guard by Castles reappearance in her life, wonders if shes marrying the right guy. With the nuptials forestalled and the entire wedding party under suspicion, Beckett questions Castles ability to be objective about the case. But when it looks to Beckett like Castle and Kyra might rekindle their romance, her judgment may be compromised as well.