Tom Barnaby joins the Causton Chamber of Commerce trip to Brighton as he is suspicious of dodgy mayor Hicks' plan to buy coastal land on which to buy chalets. Also opposed to the plan is Lady Matilda William,who has had threatening letters, as have the local vicar, oily property developer Hugh Dalgleish and hotelier Jenny Russell. Lady Matilda is descended from Richard of Guillaume,a ruthless contemporary of William the Conqueror,and believes that her son Richard,last of the line and brain-damaged for twenty years,was the victim of ancestral jealousy.In Brighton Dalgleish is murdered with the sword stolen from Guillaume's tomb and Hicks is arrested for fraud. Having learnt how Richard came by his accident Barnaby is convinced that Richard and not the property scam is the cause of yet another victim being claimed by the sword of Guillaume. 　　译文(3): 汤姆·巴纳比（Tom Barnaby）加入了考斯顿商会（Causton Chamber of Commerce）对布莱顿的访问，因为他对狡猾的市长希克斯（Hicks）购买沿海土地购买小屋的计划持怀疑态度。同样反对该计划的还有玛蒂尔达·威廉夫人，她收到了恐吓信，当地牧师、油性房地产开发商休·达尔格里什和酒店经营者珍妮·拉塞尔也收到了恐吓函。玛蒂尔达夫人是纪尧姆的理查德的后裔，纪尧姆是征服者威廉的同时代无情的人，她认为她的儿子理查德是祖先嫉妒的受害者，理查德是最后一个，大脑受损了20年。在布莱顿，达尔格里什被从纪尧姆墓中偷来的剑谋杀，希克斯因欺诈被捕。Barnaby了解到Richard是如何遭遇事故的，他确信Richard而不是财产骗局是另一名受害者被纪尧姆之剑夺走的原因。