| 1 | Hercule | Poirot | The famous detective. |
| | George | | Hercule's valet. |
| | Arthur | Hastings | Hercule's friend. |
| | Mrs. | Oliver | Hercule's friend. |
| | Claud | Amory | Famous scientist. Hercule's client. aka: Sir Claud. |
| | | | Abbot's Cleve - Sir Claud's house. |
| | Tredwell | | Sir Claud's butler. |
| | Richard | Amory | Sir Claud's only son. |
| | Barbara | Amory | Richard's cousin. Sir Claud's niece. |
| | Dr. | Carelli | Lucia's Italian house guest. |
| | Caroline | Amory | Sir Claud's sister. aka: Aunt Caroline, Miss Amory. |
| | Edward | Raynor | Sir Claud's secretary. |
| | Lucia | Amory | Richard's wife. |
| | Jackson | | Garage owner. |
| 3 | Algernon | | Barbara's great uncle. |
| | Ellen | | Sir Claud's servant. |
| | Edna | Amory | Barbara's sister. Dispensary at the county hospital. |
| 6 | Kenneth | Graham | Sir Claud's physician. |
| 12 | Aloysius | Jones | Caroline's former lover. |
| 13 | Selma | Goetz | Most successful international spy. |
| | Vittoria | Muzio | Lucia's servant. |
| 14 | Inspector | Japp | Police inspector from Scotland Yard. |
| 15 | Constable | Johnson | Inspector Japp's assistant. |
| | Baron | Altara | Criminal. |
| 16 | Miguel | | Dr. Carelli's friend. |
| 18 | Lord | Edgware | Hercule's former client. |
