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 organization known only as Nightingale is the ongoing focus of the eight episodes. And Lucas' relationship with CIA agent Sarah Caulfied (Genevieve O'Reilly), reignites concerns over his loyalty. This season also sees the exit of one of the few original cast members, Malcolm Wynn-Jones.