1949年5月，人民解放军解放上海之际，中共上海地下党负责人叶正龙获悉，国民党特务组织企图炸毁我上海沪江发电厂，此企图被国民党特务组织命名为“萤火虫计划”。为了粉碎萤火虫计划，上海市公安局侦察科在科长叶正龙的带领下，和国民党特务组织斗智斗勇，展开了一系列的侦破工作，并积极设计，建设地下应急发电组。在工作过程中，出现了国民党特务组织蓄谋制造的破坏事件。经过一番努力，叶正龙不负众望，最终揪出了隐藏在我上海市公安局内部，代号为“老鹰”的国民党特务，并粉碎了国民党特务组织的“萤火虫计划”。
Having woken up in Hong Kong, with no memory for the last two years (!), Sydney returns to Los Angeles to try to piece together the last two years of her life and discovers the fates of her friends and family: Vaughn has married thinking that Sydney was long dead; Marshall is having a baby with CIA tech expert Carrie Bowman; and Dixon is now the new division head of the L.A. office branch of the CIA. Sydney also learns the shocking fates of Jack and Sloane; the former is in CIA custody for communicating with Irina whom still is in hiding, while the latter is living in Switzerland under house arrest in exchange for co-operation with the CIA. Sydney is granted temporary CIA clearance on a case that may help her regain her memory and she meets a new enemy group called The Covenant.
诸葛一家本过着中产生活，直至长子诸葛靖瞒着家人，毅然辞去经理一职，成立家居清洁公司，更被拍档骗去资本。靖的母亲黎嘉嘉虽感震怒，但因靖一向听话，仍动员全家一起当上家务助理。虽疲于奔命，但大家都毫无怨言。可是此时，嘉却发现自己患上绝症，由照顾者变成被人照顾，嘉终明白互相尊重的重要，更开始反思自己与子女的相处之道……
