Japp snorted slightly at the word "psychology," which he disliked and mistrusted.

"That's the sort of stuff M. Poirot likes to hear," he said.

"I am very interested, yes, in what you both say."

"You don't doubt that she was killed that way, I suppose?" Japp asked him suspiciously. "I know your tortuous mind."

"No, no, my friend. My mind is quite at ease on that point. The poisoned thorn that I picked up was the cause of death - that is quite certain. But, nevertheless, there are points about this case -"

He paused, shaking his head perplexedly.

Japp went on:

"Well, we get back to our Irish stew, we can't wash out the stewards absolutely, but I think myself it's very unlikely that either of them had anything to do with it. Do you agree, M. Poirot?"

"Oh, you remember what I said. Me, I would not wash out - what a term, mon Dieu! - anybody at this stage."

"Have it your own way. Now, the passengers. Let's start up at the end by the stewards' pantry and the wash rooms. Seat No. 16." He jabbed a pencil on the plan. "That's the hairdressing girl, Jane Grey. Got a ticket in the Irish Sweep - blewed it at Le Pinet. That means the girl's a gambler. She might have been hard up and borrowed from the old dame; doesn't seem likely either that she borrowed a large sum, or that Giselle could have a hold over her. Seems rather too small a fish for what we're looking for. And I don't think a hairdresser's assistant has the remotest chance of laying her hands on snake venom. They don't use it as a hair dye or for face massage.

"In a way, it was rather a mistake to use snake venom; it narrows things down a lot. Only about two people in a hundred would be likely to have any knowledge of it and be able to lay hands on the stuff."

"Which makes one thing, at least, perfectly clear," said Poirot.

It was Fournier who shot a quick glance of inquiry at him.

Japp was busy with his own ideas.

"I look at it like this," he said. "The murderer has got to fall into one of two categories. Either he's a man who's knocked about the world in queer places - a man who knows something of snakes, and of the more deadly varieties, and of the habits of the native tribes who use the venom to dispose of their enemies. That's Category No. 1."

"And the other?"

"The scientific line. Research. This boomslang stuff is the kind of thing they experiment with in high-class laboratories. I had a talk with Winterspoon. Apparently, snake venom - cobra venom, to be exact - is sometimes used in medicine. It's used in the treatment of epilepsy with a fair amount of success. There's a lot being done in the way of scientific investigation into snake bite."

"Interesting and suggestive," said Fournier.