Nathan Fillion and Stana Katic star as Richard Castle and Kate Beckett, the mystery crime writer turned sleuth and New York detective, in the explosive new season of the top-rated US crime drama.
Whether they’re chalk and cheese or yin and yang...
These women rule the roost when it comes to on-screen sleuthing.
The pain is real.
It was tough, but we'll get through it together.
Are you a loyal Castle viewer? Take our quick-fire quiz to find out how much you know.
Whether your favourite is Backett, Castle, Ryan or Martha, find out what makes them tick.