|Till Death Do Us Part|
|Season 4, Episode 11|
|Air date||January 9, 2012|
|Written by||Jeff Bleckner|
|Directed by||David Grae|
When a Lothario is killed, Castle and Beckett suspect that the victim's mysterious double life holds the key to his murder. Their investigation leads to a shocking twist that threatens to disrupt Ryan's wedding with Jenny.
- Nathan Fillion as Richard Castle
- Stana Katic as Detective Kate Beckett
- Jon Huertas as Detective Javier Esposito
- Seamus Dever as Detective Kevin Ryan
- Tamala R. Jones as Dr. Lanie Parish
- Penny Johnson Jerald as Captain Victoria Gates
- Molly C. Quinn as Alexis Castle
- Susan Sullivan as Martha Rodgers
- Jaime Ray Newman as Holly Franklin
- Sam Hennings as Seth Harris
- Juliana Dever as Jenny Duffy O'Malley
- Mo Mandel as Max Landon
- Desmin Borges as Pablo Barnes
- Jenna Gering as Lisa Hill
- Parisa Fakhri as Colette Roth
- Brian D. Johnson as Ron Hill
- Donald Agnelli as Barry
- Donna Feldman as Jody Garcia
- Timon Kyle as Toby Lang
- Crystal Coney as Judy Doyle
- Tammy Felice as Sexy Woman #1
- Kristina Geddes as Sexy Woman #2
- Byrne Offutt as Manager
- Lindsay LaVanchy as Assistant
- Haley Strode as Hot Young Woman
- Daniel Romer as Cute Young Guy
- Wendy Benson-Landes as Amy Kemp (uncredited)
- Beckett: Looks like he did the deed before taking the dive.
- Castle: Last item on your bucket list?
- Beckett: Castle, if we were getting married, would you want to know about all the guys I've slept with?
- Castle: All?
- Beckett: Are you really asking for my number?
- Castle: You show me yours, I’ll show you mine.
- "Bolero" by Ravel
- In the 9th eposide, Season 1 ("Little Girl Lost") Castle makes fun of Ryan's tie and he reveals that it was a gift from his girlfriend for their two-week anniversary.
- This is the second wedding that both Castle and Beckett went to; the first was that of Castle's ex-girlfriend Kyra in "A Rose for Everafter".