谢斯塔公主(阿玛拉·卡兰 Amara Karan 饰)的到来让芳草地女子学校蓬荜生辉,她即将成为这里的一名学生。作为校长,布尔斯特罗德女士(哈丽特·瓦尔特 Harriet Walter 饰)对接下来的一个学期充满了期待,除了谢斯塔公主外,詹妮弗(乔·伍德考克 Jo Woodcock 饰),茱莉亚(Lois Edmett 饰)等名门闺秀的存在让她相信,自己一手创办的学校会越来越好。 随着时间的推移,一些问题和矛盾暴露了出来,校园中的气氛逐渐紧张了起来。斯普林杰小姐(Elizabeth Berrington 饰)的死亡让学生和老师们陷入了恐慌,随后,谢斯塔公主遭到了绑架。在一连串打击之下,茱莉亚和詹妮弗意识到她们正处于危险之中,两人找来了大侦探波洛(大卫·苏切特 David Suchet 饰),希望通过他的智慧找到最终的真相。When the middle-Eastern country of Ramat is over-run by anti-monarchist revolutionaries, the surviving heir to the throne, Princess Shaista, is spirited away to safety in a small girls' school, Meadowbank, which is run by the progressive Miss Bulstrode. However, when the bullying games mistress Miss Springer is found stabbed through the chest with a javelin, it appears that Meadowbank may not be the haven it promised to be. As Poirot assists Inspector Kelsey, they begin to find that some of the staff may not be quite what they appear, a situation which is compounded when another teacher, Mademoiselle Blanche is found dead and Princess Shaista is kidnapped from the school. With the princess' life in peril, and the prized rubies of Ramat missing, it is up to Poirot to discover who is the cat among the pigeons.