| Captain Hastings | | The third victims profession. |
| Chief Inspector Japp | | The first victim's profession. |
| Crime Novel | | The Belgian detective udes these words as another name for his brains |
| Alexander Bonaparte Cust | | Before each victim died, they bought a pair of these from a door-to-door salesman. |
| Clues | | Mr._ _ _ _ _ _ _ _ _ _'s murder didn't fit the picture |
| Megan Barnard | | The Belgian detective sometimes speaks this language in the book. |
| Donald Fraser | | The (rich) third victim. |
| Waitress | | The Belgian detective's long-time friend and assistant. |
| Rail | | The niece of the first victim. |
| Bexhill | | The third murder occured in this city. |
| Earlsfield | | The ABC _ _ _ _ Guide was left beside each murdered body. |
| Thora Grey | | The self-confessed murderer and a salesman who visited the victims shortly before their murders. His initials are A.B.C. |
| Archaeologist | | These helped with solving the murder mystery. |
| Andover | | The little, Belgian detective with and egg-shaped head and a moustache. |
| Sir Carmichael Clarke | | The jealous boyfriend of the second victim. |
| Betty Barnard | | The place where the first murder was comitted. |
| Typewriter | | The first victim's name. |
| Hercule Poirot | | The ABC letters written to the detective were written using this machine. |
| French | | The estranged husband of the first victim. |
| little grey cells | | The second victim was called _ _ _ _ _ _ _ _ _ _ _ _. |
| Merchant | | The self-confessed murderer suffers from this. |
| Alphabet | | The attractive secretary to the third victim. |
| Mary Drower | | The sister of the second victim. |
| Epilepsy | | The town where the second murder had taken place. |
| Franklin Clarke | | This man is always one step behind the Belgian detective. |
| Franz Ascher | | The fourth and final murder happened here. |
| Churchston | | The order of which the victims were murdered. |
| Stockings | | The second victim's profession. |
| Alice Ascher | | The brother of the third victim. But was that all he was? |
| Doncaster | | The genre of this book. |