As of September 2015, the television series "Castle" has not been cancelled. The eighth season of the show is set to premiere on September 21, 2015, on ABC.
ABC intends to broadcast "Castle" in its previous slot of 10 p.m. eastern time and 9 p.m. central time, and the show is set for 22 episodes. Its seventh season finale had the lowest ratings for a "Castle" season finale in the series' history with only 8.44 million people tuning in, which dipped below the first season finale that only brought in 9.96 million viewers. The season seven premiere performed decently with 10.75 million viewers, making it the fourth most viewed premier in the series' history, the median of the seven premieres.
The series continues to follow Richard Castle, a famous mystery novelist, and Kate Beckett, a New York City detective. While suffering a severe case of writer's block, Richard Castle is brought in by the police for questioning after a copycat murder based on one of Castle's crime novels occurs. Castle uses this opportunity to shadow Detective Kate Beckett as she attempts to solve the case. While Beckett is initially opposed to the idea, she eventually realizes that Castle is a useful resource, and the two characters ultimately develop deeper feelings for each other.