"I say, Alexandre, perhaps you're not dead, but you're certainly very green."

Mazeroux gave a wry laugh:

"Upon my word, Chief, I confess that I had a bad time of it when I was keeping watch while you were asleep."

"Were you afraid?"

"To the roots of my hair. I kept on thinking that something was going to happen. But you, too, Chief, don't look as if you had been enjoying yourself. Were you also--"

He interrupted himself, on seeing an expression of unbounded astonishment on Don Luis's face.

"What's the matter, Chief?"

"Look! ... on the table ... that letter--"

He looked. There was a letter on the writing-table, or, rather, a letter-card, the edges of which had been torn along the perforation marks; and they saw the outside of it, with the address, the stamp, and the postmarks.

"Did you put that there, Alexandre?"

"You're joking, Chief. You know it can only have been you."

"It can only have been I ... and yet it was not I."

"But then--"

Don Luis took the letter-card and, on examining it, found that the address and the postmarks had been scratched out so as to make it impossible to read the name of the addressee or where he lived, but that the place of posting was quite clear, as was the date: Paris, 4 January, 19--.

"So the letter is three and a half months old," said Don Luis.

He turned to the inside of the letter. It contained a dozen lines and he at once exclaimed:

"Hippolyte Fauville's signature!"

"And his handwriting," observed Mazeroux. "I can tell it at a glance.

There's no mistake about that. What does it all mean? A letter written by Hippolyte Fauville three months before his death?"

Perenna read aloud:

"MY DEAR OLD FRIEND:

"I can only, alas, confirm what I wrote to you the other day: the plot is thickening around me! I do not yet know what their plan is and still less how they mean to put it into execution; but everything warns me that the end is at hand. I can see it in her eyes. How strangely she looks at me sometimes!

"Oh, the shame of it! Who would ever have thought her capable of it?

"I am a very unhappy man, my dear friend."

"And it's signed Hippolyte Fauville," Mazeroux continued, "and I declare to you that it's actually in his hand ... written on the fourth of January of this year to a friend whose name we don't know, though we shall dig him out somehow, that I'll swear. And this friend will certainly give us the proofs we want."

Mazeroux was becoming excited.

"Proofs? Why, we don't need them! They're here. M. Fauville himself supplies them: 'The end is at hand. I can see it in her eyes.' 'Her'

refers to his wife, to Marie Fauville, and the husband's evidence confirms all that we knew against her. What do you say, Chief?"

"You're right," replied Perenna, absent-mindedly, "you're right; the letter is final. Only--"

"Only what?"

"Who the devil can have brought it? Somebody must have entered the room last night while we were here. Is it possible? For, after all, we should have heard. That's what astounds me."

"It certainly looks like it."

"Just so. It was a queer enough job a fortnight ago. But, still, we were in the pa.s.sage outside, while they were at work in here, whereas, this time, we were here, both of us, close to this very table. And, on this table, which had not the least sc.r.a.p of paper on it last night, we find this letter in the morning."

A careful inspection of the place gave them no clue to put them on the track. They went through the house from top to bottom and ascertained for certain that there was no one there in hiding. Besides, supposing that any one was hiding there, how could he have made his way into the room without attracting their attention? There was no solving the problem.

"We won't look any more," said Perenna, "it's no use. In matters of this sort, some day or other the light enters by an unseen cranny and everything gradually becomes clear. Take the letter to the Prefect of Police, tell him how we spent the night, and ask his permission for both of us to come back on the night of the twenty-fifth of April. There's to be another surprise that night; and I'm dying to know if we shall receive a second letter through the agency of some Mahatma."

They closed the doors and left the house.

While they were walking to the right, toward La Muette, in order to take a taxi, Don Luis chanced to turn his head to the road as they reached the end of the Boulevard Suchet. A man rode past them on a bicycle. Don Luis just had time to see his clean-shaven face and his glittering eyes fixed upon himself.

"Look out!" he shouted, pushing Mazeroux so suddenly that the sergeant lost his balance.

The man had stretched out his hand, armed with a revolver. A shot rang out. The bullet whistled past the ears of Don Luis, who had bobbed his head.

"After him!" he roared. "You're not hurt, Mazeroux?"

"No, Chief."

They both rushed in pursuit, shouting for a.s.sistance. But, at that early hour, there are never many people in the wide avenues of this part of the town. The man, who was making off swiftly, increased his distance, turned down the Rue Octave-Feuillet, and disappeared.

"All right, you scoundrel, I'll catch you yet!" snarled Don Luis, abandoning a vain pursuit.

"But you don't even know who he is, Chief."

"Yes, I do: it's he."

"Who?"

"The man with the ebony stick. He's cut off his beard and shaved his face, but I knew him for all that. It was the man who was taking pot-shots at us yesterday morning, from the top of his stairs on the Boulevard Richard-Wallace, the one who killed Inspector Ancenis. The blackguard! How did he know that I had spent the night at Fauville's?

Have I been followed then and spied on? But by whom? And why? And how?"

Mazeroux reflected and said:

"Remember, Chief, you telephoned to me in the afternoon to give me an appointment. For all you know, in spite of lowering your voice, you may have been heard by somebody at your place."

Don Luis did not answer. He thought of Florence.

That morning Don Luis's letters were not brought to him by Mlle.