| Detective | Barnes | A detective at Scotland Yard. |
| Captain | Daniels | One of Mr. MacAdam's secretaries. |
| Miss | Daniels | Mr. MacAdam's aunt. |
| Bernard | Dodge | A member of the War Cabinet. |
| Lord | Estair | The leader of the House of Commons. |
| Mrs. | Everard | Mr. MacAdam's aunt. |
| Arthur | Hastings | Narrator. A police captain. |
| Captain | Lyall | The young pilot. |
| David | MacAdam | The Prime Minister of England. |
| Major | Norman | Detective Barnes's colleague. |
| Hercule | Poirot | The famous Belgian detective. Hasting's close friend. |
| John | Smith | The farmer of Clapham. |
| Edith | | The little girl at the burglar's house. |
| Japp | | Poirot's acquaintance. The Chief Inspector. |
| O'Murphy | | Mr. MacAdam's chauffeur. |
