Nathan Fillion as Richard Castle and Stana Katic as Kate Beckett in ABC crime drama 'Castle'.Facebook/Castle

The cast and crew of "Castle" Season 8 will take viewers through a roller coaster of events, with some surprising changes in Richard Castle (Nathan Fillion), Kate Beckett (Stana Katic), Kevin Ryan (Seamus Dever) and Javier Esposito's (Jon Huertas) lives.

While the mystery novelist will once again take up the role of a new investigator, the detectives will face some ups and downs in their professional as well as personal lives.

The upcoming season of ABC crime drama will begin with a two-hour special premiere, which will mainly focus on Fillion's character and his first case. He will dig up his past while investigating his father's disappearance. During the process, he will recollect a few things that led to his own disappearance, according to Fashion & Style.

"This year, we really do want to get into what happened when he was gone in a way that hopefully ties a lot of the threads of mysteries of seven seasons together in an unexpected and exciting way," Entertainment Weekly quoted showrunner Alexi Hawley as saying.

In the meantime, Dever's character and his wife will receive a good news, which will apparently lead to a feud between Ryan, Beckett and Esposito.

Creator Terence Paul Winter recently revealed that a baby is on the way for Jenny Ryan (Juliana Dever) and her partner. "Ultimately, that's going to make Ryan even more paranoid and more excited about trying to make more money. When he sees Beckett rising up in the ranks, the boys realise it's time for them to start looking at their futures, which is going to create some tension and conflict between them," Winter told TV Guide.

However, the fans of the popular on-screen power couple do not have to be worried about the future of their favourite characters as the executive producer stated that "Castle" Season 8 will mainly revolve around their romance.

Winter said, "It's always been about the Castle-Beckett love story. That's steeped in the DNA of the show, and that's what it will always be. Now, it's about exploring the next evolution of it. How do we deepen that love story? What challenges can we put their way that can put their romance at a much higher, different place?" 

ABC will premiere "Castle" Season 8 on Monday, 21 September, at 9 pm.