‘Was—was there really danger? What was there in the syringe?’

Japp said:

‘Will you explain, or shall I?’

Poirot said gravely:

‘Mademoiselle, this Dr Andersen had perfected a scheme of exploitation and murder—scientific murder. Most of his life has been spent in bacteriological research. Under a different name he has a chemical laboratory in Sheffield. There he makes cultures of various bacilli. It was his practice, at the Festivals, to inject into his followers a small but sufficient dose of Cannabis Indica—which is also known by the names of Hashish or Bhang. This gives delusions of grandeur and pleasurable enjoyment. It bound his devotees to him. These were the Spiritual Joys that he promised them.’

‘Most remarkable,’ said Miss Carnaby. ‘Really a most remarkable sensation.’

Hercule Poirot nodded.

‘That was his general stock in trade—a dominating personality, the power of creating mass hysteria and the reactions produced by this drug. But he had a second aim in view.

‘Lonely women, in their gratitude and fervour, made wills leaving their money to the Cult. One by one, these women died. They died in their own homes and apparently of natural causes. Without being too technical I will try to explain. It is possible to make intensified cultures of certain bacteria. The bacillus Coli Communis, for instance, the cause of ulcerative colitis. Typhoid bacilli can be introduced into the system. So can the Pneumococcus. There is also what is termed Old Tuberculin which is harmless to a healthy person but which stimulates any old tubercular lesion into activity. You perceive the cleverness of the man? These deaths would occur in different parts of the country, with different doctors attending them and without any risk of arousing suspicion. He had also, I gather, cultivated a substance which had the power of delaying but intensifying the action of the chosen bacillus.’

‘He’s a devil, if there ever was one!’ said Chief Inspector Japp.

Poirot went on:

‘By my orders, you told him that you were a tuberculous subject. There was Old Tuberculin in the syringe when Cole arrested him. Since you were a healthy person it would not have harmed you, which is why I made you lay stress on your tubercular trouble. I was terrified that even now he might choose some other germ, but I respected your courage and I had to let you take the risk.’

‘Oh, that’s all right,’ said Miss Carnaby brightly. ‘I don’t mind taking risks. I’m only frightened of bulls in fields and things like that. But have you enough evidence to convict this dreadful person?’

Japp grinned.

‘Plenty of evidence,’ he said. ‘We’ve got his laboratory and his cultures and the whole layout!’

Poirot said:

‘It is possible, I think, that he has committed a long line of murders. I may say that it was not because his mother was a Jewess that he was dismissed from that German University. That merely made a convenient tale to account for his arrival here and to gain sympathy for him. Actually, I fancy, he is of pure Aryan blood.’