 Poirot is excited when Belgian s greatest film star contacts him to meet while she is in London. But when he arrives he finds her terrified by a series of threatening notes hand delivered to the hotel s front desk from a Chinese man, stating that a precious diamond she owns will be stolen. The next day, Poirot receives a call from another woman who owns a duplicate diamond, stating that she too has received threatening notes, but this time through the post. When both diamonds disappear, it leads Poirot to cross path with an adulterous, thieving husband of one of the woman, and a rather shady German businessman who likes to collect diamonds for his private collection -- and he doesn t care how the person who has them comes into possession of the diamonds.