Season 3, Episode 6
Air date October 25, 2010
Written by David Amann
Directed by Bill Roe
Episode guide
Anatomy of a Murder
Almost Famous
Castle season 3 cast
Season 3
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Season 2   Season 4

3XK is the sixth episode of the third season of Castle, and the fortieth overall.


When a woman's dead body shows signs of an old killer's handiwork, Castle and Beckett discover that the Triple Killer, a murderer who vanished four years prior, may have returned. Meanwhile, Alexis has a secret admirer.



Castle S03E06 '3XK' Promo

Castle S03E06 '3XK' Promo


Main Cast

Guest Stars


Castle: You heard the man! Put your hands in the air and get on your knees while you're at it!
Beckett: Tell me something, Castle. Why did he let you live?
Castle: To punish me. Make me pay for ruining his plan. Now he’s going to kill again, all because I couldn't stop him. And I feel so …
Beckett: I know the feeling.
Castle: I know you do.
Montgomery: ...The Feds say he's a white male, 25 to 35 years old...
Castle: Could be me
Montgomery: ..with a dysfunctional relationship with his mother...
Castle : Still me
Montgomery: ..he has a menial, unimportant job...
Beckett: Definitely you
Castle: Just for that I base my next book on Esposito

Featured Music

  • "Without You" by Derek Evry
  • "A Million Ways" by Uncle Lucius


  • Foreshadowing: Beckett writes Tyson's name down after talking to prison officials about Gates's known associates. Castle mis-reads her handwriting as "Jelly Tyson" and before leaving to meet Tyson, he corrects the spelling on her pad. This foreshadows Castle realizing the mistaken identity of the Triple Killer.
  • The seedy motel where the police have housed Jerry Tyson has a pool. While common in L.A., where Castle is filmed, this is almost unheard of in New York City, for reasons of climate and real estate expense.
  • It was never explained where Jerry got the $100,000 to pay for Paul's operation.
  • Each of the people questioned on-camera in this episode is guilty of at least some of the Triple Killer murders: Paul McCardle, Marcus Gates, and Jerry Tyson.
  • Castle's cell phone image of his mother is a publicity still of her from when she was much younger.
  • Beckett holds hands with Castle to comfort him. This is the first time they've held hands. She also brings him coffee for a change.
  • Ryan's gun, stolen in this episode, reappears in "Kick the Ballistics".