ABC's "Castle" returns for its sixth season this September. The premiere episode, "Valkyrie," of "Castle" Season 6 is the most awaited episode for millions of Caskett (Castle + Beckett) shippers as "Castle" Season 5 final episode ended on Rick's (Nathan Fillion) marriage proposal.

Castle, the writer of mystery best sellers, finally went down on one of his knees and proposed to Kate Beckett (Stana Katic), "Katherine Houghton Beckett, will you marry me?"

There is a "definite" answer and Detective Beckett is not going to take time to answer the proposal, according to reports. Also, she is likely to reveal to Castle that she is going to take-up the Washington DC job offer, which she actually takes-up and moves to Washington DC. There is nothing to worry about on the proposal front as the possibility is quite high that she is going to accept the job offer as well as the marriage proposal.

Castle in New York and his possible fiancé, Beckett, in Washington DC will provide for endearing as well as frustrating moments. Also, there is a new mentor of Beckett in picture. Lisa Edelstein is reportedly going to portray the role of Beckett's mentor, Rachel McCord and the reports suggest that, she is not going to be happy about Beckett's relationship with Castle.

The leaked audition video of the actor playing Pi (Myko Olivier), Alexis (Molly Quinn) new friend, alludes to things not going great between Castle and his fiancé Beckett. Beckett's new mentor may likely to be one of the reasons for the not so smooth sailing relationship after Beckett agrees to Castle proposal.

Edelstein had said to TV Guide that "What McCord's done with her life is really inspiring and tempting to Beckett, but it is also threatening to the way of life Beckett's chosen so far."

Whatever is the answer and whatever turns the new season takes, romance is likely to be integral to "Castle" Season 6. There is "dramatic consequences" for Beckett, according to Andrew Marlow, "Castle" showrunner.

"If she says yes to the proposal, there is a whole series of consequences in that relationship that are going to arise. But if she says no to the proposal, again, how is that going to affect the relationship? If she says yes to the job in D.C., it's going to fundamentally alter stuff for Beckett and Castle. And if she says no to it, is Beckett betraying who she is as a person and will she be able to live with that? We're really excited to explore the dramatic opportunities, no matter which ways the questions are answered,"Marlow said in an interview with Give Me My Remote.

ABC's "Castle" Season 6 premieres on September 23, 2013, with the episode "Valkyrie.