CASTLE - "XX" - In part two of last week's Season 8 premiere, Beckett's side of her abrupt disappearance is revealed. After receiving a mysterious tip from her past, Beckett is launched into a fight for her life, with a team of mercenaries hot on her trail. While Castle investigates why his wife is on the run, Beckett must figure out who wants her dead, before they can finish the job. "XX" will air on MONDAY, SEPTEMBER 28 (10:01-11:00 p.m. ET/PT) on the ABC Television Network. (ABC/Richard Cartwright) STANA KATIC, NATHAN FILLION