When does Castle return?

The series was produced jointly by Beacon Pictures and ABC Studios. It aired on ABC for a total of eight seasons from March 9, 2009, to May 16, 2016. It primarily traces the lives of Richard Castle (Nathan Fillion), a best-selling mystery novelist, and Kate Beckett (Stana Katic), a homicide detective. The overarching plot of the series focused on the romance between the two lead characters and their ongoing investigation of the murder of Beckett's mother.
Richard Castle (Fillion) is a famous mystery novelist. He is brought in by the New York Police Department for questioning regarding a copycat murder based on one of his novels. He meets and becomes intrigued by Detective Kate Beckett (Katic), the officer assigned to the case. The two eventually become friends and then lovers.