The fourth season of American crime-comedy-drama television series Castle was ordered on January 10, 2011, by ABC.

[3] Penny Johnson Jerald joined the cast as the new captain, Victoria "Iron" Gates for the fourth season.

[4] Richard Castle (Fillion) is a famous mystery novelist who has killed off the main character 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).

Castle decides to use Beckett as his muse for Nikki Heat, the main character of his next book series.