"You and I are done professionally."
As Castle learns more and more about his new muse, the murder of Beckett's mother remains a mystery. When Castle asks Beckett about her mom, she immediately gets hostile. She almost lost herself trying to solve the case and warns Castle that if he even blinks in that direction, their partnership is done.
But Castle being Castle goes behind her back and ends up finding some new information about the case. After a heart-to-heart with his mother, Castle tells Beckett what he's done. Sadly for him, Detective Kate Beckett is a woman of her word. She informs Castle that they are finished. Anyone else wish our favorite author could write a happier ending to this particular story?