乔尔·拉撒路（山姆·克拉弗林 饰）的父亲乔纳森·拉撒路博士（比尔·奈伊 饰）自杀身亡，他很快就被卷入了一系列谋杀悬案之中，同时他还在努力揭开父亲之死和25年前妹妹的死亡之谜。
落榜才子石玉昆来到老北京的天桥，以弹唱单弦为生，并希望能成就一番事业。在这里他遇到了武艺高超的懒猫“展昭”、牙尖嘴利满肚子鬼点子的白玉堂、秀美灵巧的丁氏姐妹、口技了得的小艾虎，还有身怀绝技的五鼠。石玉昆热心机敏，他机巧地帮助大家伸张正义，并与大家结成了生死兄弟。各怀绝技的“十三郎”屡破奇案，成为北京市井民众心中的“包青天”……石玉昆假借包拯为主角，将他们破案的真实过程写成了小说，这就是千古传诵的《七侠五义》！
As Leo's replacement Thomas Chamberlain arrives Nikki investigates the murders of Rachel Freedman, shot in the head, and her little autistic son Nathan, who was poisoned. Nikki rejects policewoman Anne Burchett's theory that Rachel killed them both but is perturbed when an impostor, claiming to be Rachel's sister, visits the morgue. At the same time the disfigured corpse of Eva Liron is discovered, killed with the same poison as Nathan. She had been the nanny to French hot shot footballer Isaac Dreyfus and was planning to blackmail him over a sex tape of them both. Jewish Isaac is a controversial figure due to his anti-Muslim sentiments but he denies ant part in the murders. Then another victim, Isaac's agent Mousa, is discovered dead.
Shetland is BACK to answer all of the questions that left us hanging at the end of the last series.
