and attentive and that they seemed to be watching, somewhere, in space, a sight that apparently captivated them.

Meanwhile, he dictated, with intervals between each number:

"18, 9, 19, 11, 19 ..."

There was hardly anything to be seen through the window but a patch of blue sky on the right and the front of the building opposite, an old private house, whose shutters were closed as usual. There was nothing particular about all this, no detail that struck me as new among those which I had had before my eyes for years....

"1, 2...."

And suddenly I understood ... or rather I thought I understood, for how could I admit that Lupin, a man so essentially level-headed under his mask of frivolity, could waste his time upon such childish nonsense? What he was counting was the intermittent flashes of a ray of sunlight playing on the dingy front of the opposite house, at the height of the second floor!

"15, 22 ..." said Lupin.

The flash disappeared for a few seconds and then struck the house again, successively, at regular intervals, and disappeared once more.

I had instinctively counted the flashes and I said, aloud:

"5...."

"Caught the idea? I congratulate you!" he replied, sarcastically.

He went to the window and leant out, as though to discover the exact direction followed by the ray of light. Then he came and lay on the sofa again, saying:

"It's your turn now. Count away!"

The fellow seemed so positive that I did as he told me. Besides, I could not help confessing that there was something rather curious about the ordered frequency of those gleams on the front of the house opposite, those appearances and disappearances, turn and turn about, like so many flash signals.

They obviously came from a house on our side of the street, for the sun was entering my windows slantwise. It was as though some one were alternately opening and shutting a casement, or, more likely, amusing himself by making sunlight flashes with a pocket-mirror.

"It's a child having a game!" I cried, after a moment or two, feeling a little irritated by the trivial occupation that had been thrust upon me.

"Never mind, go on!"

And I counted away.... And I put down rows of figures.... And the sun continued to play in front of me, with mathematical precision.

"Well?" said Lupin, after a longer pause than usual.

"Why, it seems finished.... There has been nothing for some minutes...."

We waited and, as no more light flashed through space, I said, jestingly:

"My idea is that we have been wasting our time. A few figures on paper: a poor result!"

Lupin, without stirring from his sofa, rejoined:

"Oblige me, old chap, by putting in the place of each of those numbers the corresponding letter of the alphabet. Count A as 1, B as 2 and so on. Do you follow me?"

"But it's idiotic!"

"Absolutely idiotic, but we do such a lot of idiotic things in this life.... One more or less, you know!..."

I sat down to this silly work and wrote out the first letters:

I broke off in surprise:

"Words!" I exclaimed. "Two English words meaning...."

"Go on, old chap."

And I went on and the next letters formed two more words, which I separated as they appeared. And, to my great amazement, a complete English sentence lay before my eyes.

"Done?" asked Lupin, after a time.

"Done!... By the way, there are mistakes in the spelling...."

"Never mind those and read it out, please.... Read slowly."

Thereupon I read out the following unfinished communication, which I will set down as it appeared on the paper in front of me:

I began to laugh:

"And there you are! Fiat lux! We're simply dazed with light! But, after all, Lupin, confess that this advice, dribbled out by a kitchen-maid, doesn't help you much!"

Lupin rose, without breaking his contemptuous silence, and took the sheet of paper.

I remembered soon after that, at this moment, I happened to look at the clock. It was eighteen minutes past five.

Lupin was standing with the paper in his hand; and I was able at my ease to watch, on his youthful features, that extraordinary mobility of expression which baffles all observers and constitutes his great strength and his chief safeguard. By what signs can one hope to identify a face which changes at pleasure, even without the help of make-up, and whose every transient expression seems to be the final, definite expression?... By what signs? There was one which I knew well, an invariable sign: Two little crossed wrinkles that marked his forehead whenever he made a powerful effort of concentration. And I saw it at that moment, saw the tiny tell-tale cross, plainly and deeply scored.

He put down the sheet of paper and muttered:

"Child's play!"

The clock struck half-past five.

"What!" I cried. "Have you succeeded?... In twelve minutes?..."

He took a few steps up and down the room, lit a cigarette and said:

"You might ring up Baron Repstein, if you don't mind, and tell him I shall be with him at ten o'clock this evening."

"Baron Repstein?" I asked. "The husband of the famous baroness?"

"Yes."

"Are you serious?"

"Quite serious."

Feeling absolutely at a loss, but incapable of resisting him, I opened the telephone-directory and unhooked the receiver. But, at that moment, Lupin stopped me with a peremptory gesture and said, with his eyes on the paper, which he had taken up again:

"No, don't say anything.... It's no use letting him know.... There's something more urgent ... a queer thing that puzzles me.... Why on earth wasn't the last sentence finished? Why is the sentence...."

He snatched up his hat and stick:

"Let's be off. If I'm not mistaken, this is a business that requires immediate solution; and I don't believe I am mistaken."

He put his arm through mine, as we went down the stairs, and said:

"I know what everybody knows. Baron Repstein, the company-promoter and racing-man, whose colt Etna won the Derby and the Grand Prix this year, has been victimized by his wife. The wife, who was well known for her fair hair, her dress and her extravagance, ran away a fortnight ago, taking with her a sum of three million francs, stolen from her husband, and quite a collection of diamonds, pearls and jewellery which the Princesse de Berny had placed in her hands and which she was supposed to buy. For two weeks the police have been pursuing the baroness across France and the continent: an easy job, as she scatters gold and jewels wherever she goes. They think they have her every moment. Two days ago, our champion detective, the egregious Ganimard, arrested a visitor at a big hotel in Belgium, a woman against whom the most positive evidence seemed to be heaped up. On enquiry, the lady turned out to be a notorious chorus-girl called Nelly Darbal. As for the baroness, she has vanished. The baron, on his side, has offered a reward of two hundred thousand francs to whosoever finds his wife. The money is in the hands of a solicitor. Moreover, he has sold his racing-stud, his house on the Boulevard Haussmann and his country-seat of Roquencourt in one lump, so that he may indemnify the Princesse de Berny for her loss."

"And the proceeds of the sale," I added, "are to be paid over at once. The papers say that the princess will have her money to-morrow. Only, frankly, I fail to