Devilishly handsome detective from Scotland Yard, Simon Hunt, teams up with Castle & Beckett to find the person responsible for the murder of his friend's daughter. Also, Charles Shaughnessy plays Nigel Winthrop, the Deputy General at the British Consulate whom Castle & Beckett suspect is up to more than just ambassadorial balls and diplomatic luncheons. Meanwhile, Lanie convinces Beckett that she needs to make a move on Castle before it is too late.