Castle (Nathan Fillion) will search heaven and earth to find Kate Beckett (Stana Katic) when ABC's crime drama series returns for its eighth season.

Based on the synopsis released by the network, the premiere episode will see Beckett missing while her husband searches for her. It appears that the tables have turned for the couple, as Castle now has to track down Beckett who suddenly disappeared. Last season, she had the difficult task of finding her then fiancé when he vanished following an attempted car bombing on their wedding day.

Yahoo reports that the episode titled "XY" will be delivered via Castle's point of view. Everything will start when he receives a mysterious call from a stranger that will set off "an explosive chain of events." Soon after, his wife goes missing without a trace. Aside from Beckett's disappearance, the novelist will also have to deal with two new additions in his private investigation (PI) firm for season 8. His daughter Alexis (Molly Quinn) will be joining her father, as well as a new security specialist, Hayley Vargas (Toks Olagundoye).

Meanwhile, the show's promo reveals that just like his wife, Castle will have a new job in the upcoming installment. The International Business Times reports that the "author-turned-crime solver" will be working as "a private eye." Will his first job be to investigate the case of Beckett? Viewers now know that she turned down the opportunity to run for New York State Senate. Instead, her colleagues will have the pleasure of calling her captain.

Her promotion, however, will not dwell well on Ryan (Seamus Dever) and Esposito (Jon Huertas). Showrunner Terence Paul Winter told TV Line how this will put a wedge in their professional relationship.

"After seeing Beckett ascend the ranks, they're realizing maybe it's time for them to start looking upwards in their own careers. In doing so, they start to butt heads a bit, but in a fun way, because the dynamic between those two has always been 'two brothers," said Winter.

"Castle" season 8 will premiere on Sept. 21 at 10 p.m. EST on ABC.