"I don't know. I know nothing about her."

"But it's a mighty big proposition, eh?" suggested the other.

Poirot nodded, as he arranged the glasses in a neat

row on the tray. His love of order was as great as ever.

"What was the idea in sinking those boats? Are the

Big Four a German stunt?''

"The Big Four are for themselves--and for themselves only, M. Ie Capitaine. Their aim is world domination."

The American burst out laughing, but broke off at

the sight of Poirot's serious face.

"You laugh, monsieur." said Poirot, shaking a finger at him. "You reflect not--you use not the little gray cells of the brain. Who are these men who send a portion of your navy to destruction simply as a trial of their

power? For that was all it was. Monsieur, a test of this 46 Agatha Christie

new force of magnetical attraction which they hold."

"Go on with you, moosior," said Japp good-humouredly.

"I've read of super criminals many a time,

but I've never come across them. Well, you've heard

Captain Kent's story. Anything further I can do for

you?"

"Yes, my good friend. You can give me the address

of Mrs. Halliday--and also a few words of introduction

to her if you will be so kind."

Thus it was that the following day saw us bound

for Chetwynd Lodge, near the village of Chobham in

Surrey.

Mrs. Halliday received us at once, a tall, fair woman,

nervous and eager in manner. With her was her little

girl, a beautiful child of five.

Poirot explained the purpose of our visit.

"Oh! Monsieur Poirot, I am so glad, so thankful. I

have heard of you, of course. You will not be like these Scotland Yard people, who will not listen or try to

understand. And the French Police are just as bad-worse, I think. They are all convinced that my husband has gone off with some other woman. But he wasn't like

that! All he thought of in life was his work. Half our

quarrels came from that. He cared for it more than he

did for me."

"Englishmen, they are like that," said Poirot soothingly.

"And if it is not work, it is the games, the sport. All those things they take au grand serieux. Now,

madame, recount to me exactly, in detail, and as methodically as you can, the exact circumstances of your

husband's disappearance."

"My husband went to Paris on Thursday, the 20th of

July. He was to meet and visit various people there connected with his work, amongst them Madame Olivier."

Poirot nodded at the mention of the famous French

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THE BIO FOUR 47

woman chemist, who had eclipsed even Madame Curie

in the brilliance of her achievements. She had been

decorated by the French Government, and was one of

the most prominent personalities of the day.

"He arrived there in the evening and went at once to the Hotel Castiglione in the Rue de Castiglione. On the