Lisa Edelstein will appear on “Castle” this fall and her role will be pretty important. Edelstein will play a mentor to Beckett (Stana Katic) in connection to her job opportunity in Washington D.C. and, according to an interview the former “House” and “The Good Wife” actress did with TVGuide.com, her character—Rachel McCord—may cause some problems for our beloved couple.

"McCord becomes a mentor to Beckett and doesn't quite understand why Castle is hanging around," Edelstein said. "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."

Beckett and Castle (Nathan Fillion) have been through so much, they have to be able to overcome this right? Let’s hope.

During the sneak peek into Beckett’s proposal answer, we saw that the drama from last season will run right into this season’s premiere.

After the compilation of shock and weird faces Kate gives in response to Castle’s romantic request, she utters the words “I have something to tell you.” The safe bet is that she is going to tell him something about the D.C. job proposal. The worst possible scenario would be a straight “no,” but we can guess this isn’t the case since Rick is till “hanging around” in Season 6.

One thing we know for sure, according to TVLine.com, is that something happens at the swing set because we fast forward a few months ahead and, as Katic tells the website, things seem to be “more complicated” than the couple anticipated.

Beckett and Castle’s relationship has been the definition of up-and-down. Let’s hope they can survive Season 6.

“Castle” gets back to the small screen Monday, Sept. 23 at 10/9c on ABC.