When John ‘Ludwig’ Taylor’s (David Mitchell) identical twin, DCI James Taylor, disappears off the face of the earth, John takes over his brother’s identity in a quest to discover his whereabouts. John has never married; never had a family and never really ventured further than his own front door. Without a computer, mobile phone or even a television, he lives in quiet solitude, designing puzzles for a living, under the nom-de-plume of ‘Ludwig’. This genre bending detective series follows full-time luddite, John 'Ludwig' Taylor, as he assumes the identity of his missing twin brother in a bid to track him down and bring him home. However, filling the shoes of your identical twin is one thing - when your twin also happens to be a successful DCI leading Cambridge’s busy inner-city major crimes team the stakes are much higher. John may be a master of all things cryptic, but can he crack the biggest puzzle of his life?

故事发生在1933年的英国，声名远扬的大侦探波洛（约翰·马尔科维奇 John Malkovich 饰）收到了一封匿名信件，寄信者在信件里预言了三场谋杀，并且给出了线索。虽然波洛报了警，但警方并没有太重视这封匿名信。果不其然，凶杀案发生了，名字以“A”和“B”开头的两位被害人均被以信件中所描述的方式杀死。
波洛明白自己必须开始和时间赛跑，去拯救唯一的那一位名字以“C”开头的幸存者。之后，波洛又陆续收到了几封内容相似的匿名信，可是当他着手调查这一切事件背后的真相时，却屡屡遭到阻拦，只有克罗姆警探（鲁伯特·格林特 Rupert Grint 饰）坚定的站在波洛侦探这一边。

故事讲述刚从警察学院毕业的库尔特·维兰德(帕森饰)目睹了一场残忍的自杀式案件，在警长汉伯格(理查德·迪兰饰)的支持下，他不得不查清一系列的罪案。