- Nathan Fillion as Richard Castle
- Stana Katic as Kate Beckett
- Susan Sullivan as Martha Rodgers
- Tamala Jones as Medical Examiner Lanie Parish
- Seamus Dever
- Molly C. Quinn as Alexis Castle
- Jon Huertas
- Ruben Santiago-Hudson as Roy Montgomery
- Penny Johnson Jerald
Wildly famous mystery novelist Richard Castle (Nathan Fillion, "Desperate Housewives"), who is bored with his own success, learns that a real-world copycat killer has started staging murder scenes depicted in his novels.
Rick is soon questioned by NYPD Detective Kate Beckett (Stana Katic, "The Spirit"), a very bright, aggressive detective who keeps her investigations under tight rein. Rick and Kate's styles instantly clash, yet sparks begin to fly, leading both to danger and a hint of romance as Castle steps in to help find the killer.
And once that case is solved, he and Beckett build upon their new relationship as they look to solve strange homicides in New York - as much fun as one can have with death & murder. Castle is kept grounded by his Broadway diva mother, Martha Rodgers (Susan Sullivan, "Dharma and Greg") and quick-witted teenage daughter Alexis (Molly Quinn, "Walk Hard: The Dewey Cox Story").