‘It is a problem—yes,’ said Poirot.

‘Of course, strictly speaking, it oughtn’t to matter. We’ve got Cust on the Doncaster murder—the blood-stained coat, the knife—not a loophole there. You couldn’t bounce any jury into acquitting him. But it spoils a pretty case. He did the Doncaster murder. He did the Churston murder. He did the Andover murder. Then, by hell, he must have done the Bexhill murder. But I don’t see how!’

He shook his head and got up.

‘Now’s your chance, M. Poirot,’ he said. ‘Crome’s in a fog. Exert those cellular arrangements of yours I used to hear so much about. Show us the way he did it.’

Japp departed.

‘What about it, Poirot?’ I said. ‘Are the little grey cells equal to the task?’

Poirot answered my question by another.

‘Tell me, Hastings, do you consider the case ended?’

‘Well—yes, practically speaking. We’ve got the man. And we’ve got most of the evidence. It’s only the trimmings that are needed.’

Poirot shook his head.

‘The case is ended! The case! The case is the man, Hastings. Until we know all about the man, the mystery is as deep as ever. It is not victory because we have put him in the dock!’

‘We know a fair amount about him.’

‘We know nothing at all! We know where he was born. We know he fought in the war and received a slight wound in the head and that he was discharged from the army owing to epilepsy. We know that he lodged with Mrs Marbury for nearly two years. We know that he was quiet and retiring—the sort of man that nobody notices. We know that he invented and carried out an intensely clever scheme of systemized murder. We know that he made certain incredibly stupid blunders. We know that he killed without pity and quite ruthlessly. We know, too, that he was kindly enough not to let blame rest on any other person for the crimes he committed. If he wanted to kill unmolested—how easy to let other persons suffer for his crimes. Do you not see, Hastings, that the man is a mass of contradictions? Stupid and cunning, ruthless and magnanimous—and that there must be some dominating factor that reconciles his two natures.’

‘Of course, if you treat him like a psychological study,’ I began.

‘What else has this case been since the beginning? All along I have been groping my way—trying to get to know the murderer. And now I realize, Hastings, that I do not know him at all! I am at sea.’

‘The lust for power—’ I began.

‘Yes—that might explain a good deal…But it does not satisfy me. There are things I want to know. Why did he commit these murders? Why did he choose those particular people—?’

‘Alphabetically—’ I began.

‘Was Betty Barnard the only person in Bexhill whose name began with a B? Betty Barnard—I had an idea there…It ought to be true—it must be true. But if so—’

He was silent for some time. I did not like to interrupt him.