The eighth season of the British spy series "MI-5," which follows secret agents as they foil evil plots around the globe, begins with the fallout from Harry's kidnapping by the Russians. A mysterious anization known only as "Nightingale" is the ongoing focus of the eight episodes. And Lucas' relationship with CIA agent Sarah Caulfied (Genevieve O'Reilly), reignites ncerns over his loyalty. This season also sees the exit of one of the few original cast members, Mallm Wynn-Jones.