"I put it on your mantel-piece, governor, as usual."

Lupin's bedroom was next to the drawing-room, but Lupin had permanently bolted the door between the two. He, therefore, had to go through the hall again.

Lupin switched on the electric light and, the next moment, said:

"I don't see it..."

"Yes... I put it next to the flower-bowl."

"There's nothing here at all."

"You must be looking in the wrong place, governor."

But Achille moved the bowl, lifted the clock, bent down to the grate, in vain: the letter was not there.

"Oh blast it, blast it!" he muttered. "She's done it... she's taken it... And then, when she had the letter, she cleared out... Oh, the s.l.u.t!..."

Lupin said:

"You're mad! There's no way through between the two rooms."

"Then who did take it, governor?"

They were both of them silent. Lupin strove to control his anger and collect his ideas. He asked:

"Did you look at the envelope?"

"Yes."

"Anything particular about it?"

"Yes, it looked as if it had been written in a hurry, or scribbled, rather."

"How was the address worded?... Do you remember?" asked Lupin, in a voice strained with anxiety.

"Yes, I remembered it, because it struck me as funny..."

"But speak, will you? Speak!"

"It said, 'Monsieur de Beaumont, Michel.'"

Lupin took his servant by the shoulders and shook him:

"It said 'de' Beaumont? Are you sure? And 'Michel' after 'Beaumont'?"

"Quite certain."

"Ah!" muttered Lupin, with a choking throat. "It was a letter from Gilbert!"

He stood motionless, a little pale, with drawn features. There was no doubt about it: the letter was from Gilbert. It was the form of address which, by Lupin's orders, Gilbert had used for years in corresponding with him. Gilbert had at last--after long waiting and by dint of endless artifices--found a means of getting a letter posted from his prison and had hastily written to him. And now the letter was intercepted! What did it say? What instructions had the unhappy prisoner given? What help was he praying for? What stratagem did he suggest?

Lupin looked round the room, which, contrary to the drawing-room, contained important papers. But none of the locks had been forced; and he was compelled to admit that the woman had no other object than to get hold of Gilbert's letter.

Constraining himself to keep his temper, he asked:

"Did the letter come while the woman was here?"

"At the same time. The porter rang at the same moment."

"Could she see the envelope?"

"Yes."

The conclusion was evident. It remained to discover how the visitor had been able to effect her theft. By slipping from one window to the other, outside the flat? Impossible: Lupin found the window of his room shut.

By opening the communicating door? Impossible: Lupin found it locked and barred with its two inner bolts.

Nevertheless, a person cannot pa.s.s through a wall by a mere operation of will. To go in or out of a room requires a pa.s.sage; and, as the act was accomplished in the s.p.a.ce of a few minutes, it was necessary, in the circ.u.mstances, that the pa.s.sage should be previously in existence, that it should already have been contrived in the wall and, of course, known to the woman. This hypothesis simplified the search by concentrating it upon the door; for the wall was quite bare, without a cupboard, chimney-piece or hangings of any kind, and unable to conceal the least outlet.

Lupin went back to the drawing-room and prepared to make a study of the door. But he at once gave a start. He perceived, at the first glance, that the left lower panel of the six small panels contained within the cross-bars of the door no longer occupied its normal position and that the light did not fall straight upon it. On leaning forward, he saw two little tin tacks sticking out on either side and holding the panel in place, similar to a wooden board behind a picture-frame. He had only to shift these. The panel at once came out.

Achille gave a cry of amazement. But Lupin objected:

"Well? And what then? We are no better off than before. Here is an empty oblong, eight or nine inches wide by sixteen inches high. You're not going to pretend that a woman can slip through an opening which would not admit the thinnest child of ten years old!"

"No, but she can have put her arm through and drawn the bolts."

"The bottom bolt, yes," said Lupin. "But the top bolt, no: the distance is far too great. Try for yourself and see."

Achille tried and had to give up the attempt.

Lupin did not reply. He stood thinking for a long time. Then, suddenly, he said:

"Give me my hat... my coat..."

He hurried off, urged by an imperative idea. And, the moment he reached the street, he sprang into a taxi:

"Rue Matignon, quick!..."

As soon as they came to the house where he had been robbed of the crystal stopper, he jumped out of the cab, opened his private entrance, went upstairs, ran to the drawing-room, turned on the light and crouched at the foot of the door leading to his bedroom.

He had guessed right. One of the little panels was loosened in the same manner.

And, just as in his other flat in the Rue Chateaubriand, the opening was large enough to admit a man's arm and shoulder, but not to allow him to draw the upper bolt.

"Hang!" he shouted, unable any longer to master the rage that had been seething within him for the last two hours. "Blast! Shall I never have finished with this confounded business?"

In fact, an incredible ill-luck seemed to dog his footsteps, compelling him to grope about at random, without permitting him to use the elements of success which his own persistency or the very force of things placed within his grasp. Gilbert gave him the crystal stopper. Gilbert sent him a letter. And both had disappeared at that very moment.