Beckett has PTSD, but she also has trouble admitting that. Watch this scene from "Kill Shot" to see her attempt to deal with her condition via therapy.
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Is a sniper on the loose? Beckett and Castle examine and victim and a crime scene in this clip from "Kill Shot."
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A sniper causes major problems for the residents of New York on this episode of Castle. And for Kate Beckett herself.
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Castle Season 4 Episode 9 Quotes

Beckett: Do you know what he has that most men don't?
Castle: A Josh Groban cd?

Don't worry mother, I saw this work on Die Hard.

Rick