‘I had assumed, without pausing to consider, that what was wrong with them was the fact that they were written by a madman.

‘Now I examined them again—and this time I came to a totally different conclusion. What was wrong with them was the fact that they were written by a sane man!’

‘What?’ I cried.

‘But yes—just that precisely! They were wrong as a picture is wrong—because they were a fake! They pretended to be the letters of a madman—of a homicidal lunatic, but in reality they were nothing of the kind.’

‘It doesn’t make sense,’ Franklin Clarke repeated.

‘Mais si! One must reason—reflect. What would be the object of writing such letters? To focus attention on the writer, to call attention to the murders! En vérité, it did not seem to make sense at first sight. And then I saw light. It was to focus attention on several murders—on a group of murders…Is it not your great Shakespeare who has said “You cannot see the trees for the wood.”’

I did not correct Poirot’s literary reminiscences. I was trying to see his point. A glimmer came to me. He went on:

‘When do you notice a pin least? When it is in a pin-cushion! When do you notice an individual murder least? When it is one of a series of related murders.

‘I had to deal with an intensely clever, resourceful murderer—reckless, daring and a thorough gambler. Not Mr Cust! He could never have committed these murders! No, I had to deal with a very different stamp of man—a man with a boyish temperament (witness the schoolboy-like letters and the railway guide), an attractive man to women, and a man with a ruthless disregard for human life, a man who was necessarily a prominent person in one of the crimes!

‘Consider when a man or woman is killed, what are the questions that the police ask? Opportunity. Where everybody was at the time of the crime? Motive. Who benefited by the deceased’s death? If the motive and the opportunity are fairly obvious, what is a would-be murderer to do? Fake an alibi—that is, manipulate time in some way? But that is always a hazardous proceeding. Our murderer thought of a more fantastic defence. Create a homicidal murderer!

‘I had now only to review the various crimes and find the possible guilty person. The Andover crime? The most likely suspect for that was Franz Ascher, but I could not imagine Ascher inventing and carrying out such an elaborate scheme, nor could I see him planning a premeditated murder. The Bexhill crime? Donald Fraser was a possibility. He had brains and ability, and a methodical turn of mind. But his motive for killing his sweetheart could only be jealousy—and jealousy does not tend to premeditation. Also I learned that he had his holidays early in August, which rendered it unlikely he had anything to do with the Churston crime. We come to the Churston crime next—and at once we are on infinitely more promising ground.