Quick recap
An old, forgotten Poirot starts getting letters from A.B.C., who announces murders. Alice Asher dies in Andover and Betty Barnard in Bexhill, each with an open ABC railway guide nearby. Inspector Crome suspects Poirot himself, and stocking salesman Alexander Bonaparte Cust was close to both killings. Sir Carmichael Clarke is murdered at Churston, and in Doncaster the killer gets the wrong man. Cust, who has a brain tumor, is arrested, but Poirot sees he was used. The killer is Franklin Clarke, Sir Carmichael's brother, who wanted the title and the estate, and he's hanged. Flashbacks reveal Poirot was once a priest in Belgium.
No spoilersOpens once you mark the title as seen.