Castle has already broke ground on season 5 and we already know the premiere will have a hard focus on Beckett's mother's death and the conspiracy surrounding it. TV Line spoiled that two of the new characters involved were none other than a Senator and the Vice President.
Senator Randall Stinson and Vice President Russell — who I’m guessing will figure into the conspiracy surrounding Beckett’s mother’s murder. Note their titles. Yep, this cover-up goes all the way to the top.