On this Monday's new episode of Castle, Rick and Kate get welcomed to the FBI, while viewers welcome Jennifer Beals aboard the ABC hit.

The former Flashdance star premieres as Sophia Turner, a CIA operative from Castle's past. Meaning what, exactly?

"She became the inspiration for Clara Strike," Beals told me over the phone today. "So they were close enough that he based a book character around her."

How will Beckett react to this information? Beals made a point to say that Caskett fans don't need to worry too much about any interaction between Sophia and Castle on either of the two episodes in which she appears, but watch her opening scene below and take note of Kate's reaction:

An investigation that has "international implications," Beals teases, requiring the CIA to reach out to Beckett for help on U.S. soil.

Prepare for the first part of Castle's annual two-parter via a couple more sneak peeks, the first of which involves a VERY dead body and the second another surprise for Castle:

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.