Castle (television) ABC television series, premiering March 9, 2009 and ending May 16, 2016. Famous mystery novelist Nick Castle is bored with his own success, but when a real-world copycat murderer starts staging scenes from Nick’s novels, he is teamed up with NYPD Detective Kate Beckett to help solve the crime. Nick and Beckett’s styles instantly clash and sparks begin to fly, leading both to danger and a hint of romance. Stars Nathan Fillion (Nick Castle), Stana Katic (Kate Beckett), Molly Quinn (Alexis), Susan Sullivan (Martha), Monet Mazur (Gina), Ruben Santiago-Hudson (Capt. Montgomery). Produced by ABC Studios.