Castle follows Nathan Fillion as Richard Castle, a famous mystery novelist who is initially called in to help the NYPD solve a copy-cat murder based on his novels. Stana Katic stars opposite as the young detective Kate Beckett. Following his encounter with Beckett, Castle decides to use her as the model for the main character of his next book series. He uses his contacts and receives permission to accompany Beckett while investigating cases. While technically a drama series, Castle also features comedy and romantic tension.