Le commissaire Spence est quelqu'un d'honnête et de consciencieux. Ne vient-il pas voir Hercule Poirot, qui goûte une retraite trop tranquille, avec un immense doute à l'esprit : que l'on pende un innocent. James Bentley est accusé d'avoir tué sa logeuse, Mrs McGinty d'un coup à la tête et d'avoir volé ses économies que cette dernière cachait sous une lame de parquet. Limpide pour la plupart, cette solution est-elle réellement la bonne ? Le détective belge refera le chemin qu'avait pris le commissaire Spence, et avec l'aide de ses fameuses cellules grises, au prix d'un immense courage (il logera chez un couple bien désordonné) il mettra à jour la solution.
A revolution overthrows Prince Ali Yusuf in the Arabian country of Ramat. But before he dies, his friend manages to hide priceless jewels in the tennis racquet of Jennifer Sutcliffe, an English schoolgirl. When term begins at Meadowbank school, everyone notices the new pupil, Princess Shaista, Prince Ali Yusuf's cousin and intended bride. By rights, the jewels now belong to her but nobody knows where they are! Jennifer complains that her tennis racquet is un-useable, and swaps with her friend Julia Upjohn. Hardly a week has passed before the sadistic and unpopular games teacher, Miss Springer is found murdered in the gymnasium. Fortunately, Poirot is an old friend of the Headmistress Miss Bulstrode, and is at the school to help advise her who to choose as a successor when she retires. He is soon making progress, discovering that not everyone is quite who they say they are... First of all, he discovers that the gardener, Adam Goodman, is in fact a Secret Service Spy charged with keeping an eye on the Princess. Poirot realises that the case is somehow connected to Ramat, but how? With Miss Springer's killer still on the loose, things take a turn for the worse when Princess Shaista is kidnapped and Miss Rich, the English teacher, is attacked. However, Julia has discovered the jewels in her racquet and takes them to Poirot - he now knows what the killing is all about. Parents begin taking their children out of school and it seems things can't get any worse, when Miss Blanche the French Mistress is also found murdered in the gymnasium! But Poirot now knows who the killer is and gathers everyone together. First of all he explains that Princess Shaista was in fact an impostor, sent to the school by villains to receive the jewels should one of the dead Prince's loyal subjects try and deliver them to her. Her 'kidnap' was all staged, and the real Shaista had been kidnapped in Switzerland months earlier. He then reveals that Ann Shap