Kate Beckett is a homicide detective in the NYPD. She asks Rick Castle to help her with the case of a copy-cat killer staging murders based on scenes from his novels, and is the inspiration for Rick's new novel character, Nikki Heat.
When we first meet Beckett, she is very straightforward, conservative, and cold; however she lightens up after spending time with Rick. She resigned from the NYPD after hiding important case information from Captain Gates with Detective Esposito.
Beckett: (Clears throat) Ahem. What's the deal with men and boobs, anyway?
Castle: Biological. We can't help it.
Beckett: But doesn't it bother you that they're so obviously not real?
Castle: (Pauses) Santa's not real. We still love opening his presents.
She took my coffee, Castle!Beckett