Megan Barnard stirred in her chair.

‘Isn’t there such a thing as—as a blood lust?’ she said.

Poirot turned to her.

‘You are quite right, mademoiselle. There is such a thing. The lust to kill. But that did not quite fit the facts of the case. A homicidal maniac who desires to kill usually desires to kill as many victims as possible. It is a recurring craving. The great idea of such a killer is to hide his tracks—not to advertise them. When we consider the four victims selected—or at any rate three of them (for I know very little of Mr Downes or Mr Earlsfield), we realize that if he had chosen, the murderer could have done away with them without incurring any suspicion. Franz Ascher, Donald Fraser or Megan Barnard, possibly Mr Clarke—those are the people the police would have suspected even if they had been unable to get direct proof. An unknown homicidal murderer would not have been thought of! Why, then, did the murderer feel it necessary to call attention to himself? Was it the necessity of leaving on each body a copy of an A B C railway guide? Was that the compulsion? Was there some complex connected with the railway guide?

‘I found it quite inconceivable at this point to enter into the mind of the murderer. Surely it could not be magnanimity? A horror of responsibility for the crime being fastened on an innocent person?

‘Although I could not answer the main question, certain things I did feel I was learning about the murderer.’

‘Such as?’ asked Fraser.

‘To begin with—that he had a tabular mind. His crimes were listed by alphabetical progression—that was obviously important to him. On the other hand, he had no particular taste in victims—Mrs Ascher, Betty Barnard, Sir Carmichael Clarke, they all differed widely from each other. There was no sex complex—no particular age complex, and that seemed to me to be a very curious fact. If a man kills indiscriminately it is usually because he removes anyone who stands in his way or annoys him. But the alphabetical progression showed that such was not the case here. The other type of killer usually selects a particular type of victim—nearly always of the opposite sex. There was something haphazard about the procedure of A B C that seemed to me to be at war with the alphabetical selection.

‘One slight inference I permitted myself to make. The choice of the A B C suggested to me what I may call a railway-minded man. This is more common in men than women. Small boys love trains better than small girls do. It might be the sign, too, of an in some ways undeveloped mind. The “boy” motif still predominated.

‘The death of Betty Barnard and the manner of it gave me certain other indications. The manner of her death was particularly suggestive. (Forgive me, Mr Fraser.) To begin with, she was strangled with her own belt—therefore she must almost certainly have been killed by someone with whom she was on friendly or affectionate terms. When I learnt something of her character a picture grew up in my mind.