London 1864. On a Hackney bound train, a guard discovers blood in a first class carriage - and a body on the railway embankment. For the first time, a murder has taken place on Britain's railways. Over a hundred years later, this single documentary for BBC Two uses the first hand testimony of the people involved at the time to explore this unique event and how it provoked a huge public outcry and debate. The story quickly became a news sensation as the dangers of the brave new world of the train were laid bare. Over a hundred years later, the witnesses to this story may be long dead but their words survive in court transcripts, memoirs, letters and vivid journalism. These testimonies are now used to tell the story, taking the documentary deep into the nineteenth century to meet an extraordinary cross section of real-life Victorian London - from the engine driver who found the body to the detective in charge of the investigation. Who killed Mr Briggs?

李尔王（伊恩·麦克莱恩 Ian McKellen 饰）年事已高，他决定将广袤的国土分给自己的三个女儿科迪莉亚（萝玛拉·嘉瑞 Romola Garai 饰）、格纳利尔（弗兰西斯·巴贝 Frances Barber 饰）和里根（莫妮卡·杜兰 Monica Dolan 饰）。李尔王让三个女儿说出各自心中对父王的爱戴，格纳利尔和里根极尽花言巧语之所能，得到了李尔王的赞赏，小女儿科迪莉亚质朴而诚实，反而遭到了无情的驱逐。 失去了家园的科迪莉亚成为了法国的王后，而得到了父亲大片疆土的大女儿和二女儿则将李尔王赶出了家门。直到流落荒野无处可去，李尔王才明白自己犯了天大的错误，他一边责怪自己的愚昧，一边心痛科迪莉亚的遭遇。得知了李尔王的境遇，科迪莉亚组织了军队准备向老家进攻，不幸的是，军队遭遇惨败，科迪莉亚也遭到了逮捕。最终，科迪莉亚被处死，年迈的李尔王在痛苦中亦追随而去。