The ABC Murders was serialized in a London newspaper, the Daily Express, in the autumn of 1935, and the newspaper published simultaneously a column of ‘Readers’ Guesses’ at the solution. One reader accused Poirot of not making intelligent use of the ABC Rail Guide: ‘He is anxious to reach Churston, and so takes the midnight train from Paddington, arriving at 7.15. Had he looked more carefully, he would have found that by leaving nearly two hours later—1.40 a.m.—he would have arrived an hour earlier—at 6.10 a.m.’ But it is Hastings, not Poirot, who chooses that particular train from the ABC, and he may well have been choosing the most convenient, rather than the fastest train. ‘There’s a midnight train—sleeping-car to Newton Abbot—gets there at 6.8 a.m., and to Churston at 7.15,’ Hastings tells Poirot, adding that the ABC Rail Guide identifies Churston as a small town in Devon, 204¾ miles from Paddington, and with a population of 656. (The ABC Rail Guide ²⁶ no longer deals in fractions of a mile. It now lists Churston as being 205 miles from Paddington Station, London, with a population of 1,582. Sadly, it reveals that trains no longer run to Churston, and that the nearest British Rail station is three miles away, at Paignton. From Paignton, there is a bus service to Churston which takes fourteen minutes. The midnight train gets to Newton Abbot at 4.17 a.m., knocking 1 hour, 51 minutes off its 1935 time.)

A number of crime writers have more or less plagiarized various aspects of The ABC Murders. In Greenmask! by the American novelist, Elizabeth Linington, one of a pair of homo-sexuals is an Agatha Christie fan. He and his partner decide to make use of her ABC plot in the murders they commit: they place a copy of the relevant California county guide on the body of each victim. Ellery Queen’s Cat of Many Tails leans heavily on The ABC Murders. A French novel, The Sleeping Car Murders (filmed in 1966 with Simone Signoret and Yves Montand), was obviously inspired by Mrs Christie’s Hercule Poirot adventure.

In Chapter 3 of The ABC Murders Poirot curiously adumbrates the plot of a later Agatha Christie novel which, although she did not write it until several months after The ABC Murders, must already have been clearly formed in the author’s mind:

‘Supposing,’ murmured Poirot, ‘that four people sit down to play bridge and one, the odd man out, sits in a chair by the fire. One of the four, while he is dummy, has gone over and killed him, and intent on the play of the hand, the other three have not noticed. Ah, there would be a crime for you! Which of the four was it?’

No one can say that Agatha Christie made things easy for herself.

‘Shouldn’t wonder if you ended by detecting your own death,’ Inspector Japp says to Poirot, laughing heartily. In due course Poirot was to do precisely this, in his last and, in many ways, most extraordinary case, Curtain.