Shrewd as Nick was, he had not expected this. His first thought, as the reader knows, was that it was a bold challenge, the defiance of a nervy criminal who thought himself absolutely safe from detection.
But a moment's reflection made this seem less probable.
Was it not more natural to suppose that this event proved that the detective was unknown to the thief?
Such being the case, Colonel Richmond, his nephew and Mrs. Pond were acquitted at the start.
It may seem ridiculous to suspect them, in any case, but so strange was the nature of this affair that Nick gave nobody the credit of certain innocence.
Colonel Richmond was certainly very nearly crazy on one point. He might be so much of a lunatic as to commit these robberies from simple delusion. Or he might wish to prove to his daughter that the diamonds were not rightfully hers.
Mrs. Pond might be pawning them for small extravagances which she was afraid to have known.
As to Horace Richmond, there was no motive which seemed plausible. The value of the articles taken was so small as to make the game not worth while for a man in his position.
And it was perfectly certain that no professional thief or dishonest servant was doing the work.
If such a person had been in the game, he would not have taken one of those diamond pins; he would have taken all three.
It was impossible to lose sight of the fact that the Stevenses would be the real gainers, if this ghost business led Colonel Richmond to insist that his daughter should give up the jewels.
Mrs. Stevens and her daughter could not be doing the job personally, but they might have a secret agent among the servants, or more probably concealed in some secret recess of the strange old house.
Nick resolved to go to see Mrs. and Miss Stevens without delay. He hoped to judge by their conduct whether they knew anything about the robberies.
These thoughts passed through his mind in a flash.
He quickly searched the room to be sure that the thief was not concealed in it, and then descended to the main hall. The outer door was open, and Colonel Richmond and his daughter were standing on the steps.
Just as Nick joined them Horace Richmond strolled up. They all stood looking at a carriage which was coming up the driveway.
"Why, it's Mrs. Stevens," exclaimed Mrs. Pond. "I thought you said she did not come here any more."
"She hasn't been here in some time," responded the colonel. "I have thought that she avoided us because of this matter of the jewels."
Nothing more could be said on the subject, for at that moment the carriage drew up before the door.
Colonel Richmond advanced courteously and assisted Mrs. Stevens to alight.
Nick noticed at once that she was much agitated.
Colonel Richmond asked her into the house, but she said that she preferred to sit on the veranda. She had come on business, and would stay but a moment.
She evidently wished to speak to the colonel privately, and so the others stepped aside; but Nick's eye was upon the woman every moment.
Very few words had passed between them, when the colonel uttered a cry and called to Nick.
The detective instantly advanced. He made a sign to Richmond, but it was not understood, and the colonel introduced Nick by his right name.
"Here is an extraordinary thing, Mr. Carter," he said. "We now have proof positive that this affair is not the work of mortal hands."
"What is that?" asked Nick.
"The jewels have appeared!"
"Where?"
"In Mrs. Stevens' house. They have been mysteriously transported there without human aid."
"I should be glad to have that proven," said Nick.
"It shall be," said the colonel. "Tell your story, Mrs. Stevens, if you please."
"It is very simple," she said. "This noon, when I returned to my room after lunch, I found upon my dressing-table certain pieces of jewelry which I recognized as having belonged to the late Miss Lavina Richmond.
"I knew them well. Nothing that I can imagine could have surprised me more than to find them there. I have no explanation to offer. I can't explain how it happened."
Nick could explain it very easily, at least so far as the appearance of the jewels in that particular place was concerned. It looked like a natural development of the plot. But his face expressed no emotion as he asked:
"Who had access to that room?"
"Nobody," replied Mrs. Stevens. "It was locked."
"Is it customary for you to lock your bed-room door when you go to lunch?"
"No; it is quite unusual. But we have a new servant in the house, and, as I had considerable money in the room, I took that precaution.
"All the doors were locked. I had the key to one of them. The others were on the inside of the locks.
"When I went to lunch the jewels were not there. When I returned they were there. That is all that I know about it. Here they are."
She drew from her pocket as she spoke a small cardboard box.
The woman was making heroic efforts to be calm, but it seemed as if she might either faint or go into hysterics at any moment.
Was she playing a game that was too hard for her?
That was the question for Nick to answer; and yet, when he looked at this gentle, refined woman, he hardly had the heart to suspect her of any dishonesty.
"I will show you the jewels," she said, struggling to command her voice, "you can then see whether they are all here."
Her trembling hands could hardly find the string which was tied about the box.
While she pulled at it she kept talking as if she must do it to relieve her overburdened mind. She described the articles of jewelry which were in the box.
"They are the very ones," said the colonel.
As he uttered the words the string was loosened, and the cover fell off the box.