Castle looks rather shocked in this scene from the season two finale, doesn't he? It's courtesy of the episode "A Deadly Game."
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Castle gets together for a card game on that show's season finale. It's titled "A Deadly Game."
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Monet Mazur is back as Gina for the second season finale of Castle. She's seen here with Rick on the episode "A Deadly Game."
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Castle Season 2 Episode 24 Quotes

Now we know why our victim doesn't exist... He is a spy.

Beckett

Castle: How old would you say that kid is?
Martha: Old enough to do all the things you did at his age.