[2] Despite several other cast members having signed on for a ninth season, on May 12, 2016, it was announced that the show would be cancelled instead; the final episode aired on May 16, 2016.

[3] Richard Castle (Fillion) is a famous mystery novelist who has killed off the main character Derrick Storm in his popular book series and has writer's block.

He is intrigued by this new window into crime and murder, and uses his connection with the mayor to charm his way into shadowing Detective Kate Beckett (Katic).

[49][50] TVLine announced on July 7, 2015, that Toks Olagundoye had been added as a series regular for the eighth season, playing former Scotland Yard police officer Hayley Vargas.

[55] However, in January 2016, speculation began that the series might move on without Fillion and Katic as their contracts were due to expire again after the eighth season.

[57][58] TVLine reported on April 5, 2016, that the producers were filming multiple endings for the season in case the show was cancelled.

[62] A few days later, it was announced that Seamus Dever had signed up for a ninth season, while co-stars Jon Huertas, Molly Quinn, Susan Sullivan and Toks Olagundoye were in finalizing deals with their contracts.

[64] Despite lead actor Fillion and other cast members signing on for a potential ninth season, Castle was cancelled on May 12, 2016.