radium for you. You have a key of the door leading

from the laboratory to the garden?"

"Yes, monsieur. Here it is. I have a duplicate for

myself. And here is the key of the garden door leading

out into the alleyway between this villa and the next

one."

THE BIO FOUR 67

"I thank you, madame. To-night, go to bed as usual, have no fears, and leave all to me. But not a word to any one--not to your two assistants--Mademoiselle Claude

and Monsieur Henri, is it not?--particularly not a word

to them."

Poirot left the villa rubbing his hands in great

satisfaction.

"What are we going to do now?" I asked.

"Now, Hastings, we are about to leave Paris--for

England."

"What?"

"We will pack our effects, have lunch, and drive to theGareduNord."

"But the radium?"

"I said we were going to leave for England--I did not say we were going to arrive there. Reflect a moment,

Hastings. It is quite certain that we are being watched

and followed. Our enemies must believe that we are going back to England, and they certainly will not believe

that unless they see us get on board the train and start."

"Do you mean we are to slip off again at the last

minute?"

"No, Hastings. Our enemies will be satisfied with

nothing less than a bonafide departure."

"But the train doesn't stop until Calais?"

"It will stop if it is paid to do so."

"Oh, come now, Poirot--surely you can't pay an express to stop--they'd refuse."

"My dear friend, have you never remarked the little handle--the signale d'arret--penalty for improper use,

100 francs, I think?"

"Oh! you are going to pull that?"

"Or rather a friend of mine, Pierre Combeau, will do so. Then, while he is arguing with the guard, and making a big scene, and all the train is agog with interest,

68 Agatha Christie

you and I will fade quietly away."

We duly carried out Poirot's plan. Pierre Combeau,

an old crony of Poirot's, and who evidently knew my

little friend's methods pretty well, fell in with the arrangements. The communication cord was pulled just as

we got to the outskirts of Paris. Combeau "made a

scene" in the most approved French fashion and Poirot and I were able to leave the train without any one being interested in our departure. Our first proceeding was to make a considerable change in our appearance. Poirot

had brought the materials for this with him in a small

case. Two loafers in dirty blue blouses were the result. We had dinner in an obscure hostelry, and started back

to Paris afterwards.

It was close on eleven o'clock when we found ourselves

once more in the neighbourhood of Madame

Olivier's villa. We looked up and down the road before

slipping into the alleyway. The whole place appeared to

be perfectly deserted. One thing we could be quite certain of, no one was following us.

"I do not expect them to be here yet," whispered Poirot to me. "Possibly they may not come until tomorrow night, but they know perfectly well that there