"Sure, and this is a double mystery, so it is. What do you make of it, Mr. Van Pelt?"

It was Mrs. Kennedy who spoke. The non-appearance of Gertrude had worried her greatly, and she had visited Van Pelt, to learn that Nelson was also missing.

"I don't know what to make of it," answered George Van Pelt. "Nelson went after Billy Darnley, who robbed our stand. Perhaps he has met with foul play."

"Could our Gertrude have met with foul play at Lakewood?"

"I shouldn't think so. She knew where she was going, didn't she?"

"To be sure—to a Mrs. Broaderick's; she read the letter to me herself."

"Perhaps Mrs. Broaderick asked her to stay over," said Van Pelt. "I can't think of anything else."

While the pair were talking Mrs. Kennedy happened to look up the street.

"Here comes Nelson now!" she cried suddenly.

She was right, and soon our hero was at the stand, and shaking each by the hand.

"I feel as if I've been on a long trip," he said, with a broad smile.

"Where have you been?" questioned Van Pelt and Mrs. Kennedy in a breath, and then he told them his story, and also told of what had happened to Gertrude.

"The dirty villain!" cried Mrs. Kennedy, referring to Bulson. "He ought to be put in prison. But the poor girl's troubles are over now."

Then she told of how Mark Horton wanted his niece to come back to him.

"Perhaps he wants her back, and perhaps this is another trick," said Nelson. "After this I am going to help guard her more than ever."

"Where is she now?"

"At home. She doesn't know what to do. She thinks of calling on her uncle—to warn him against Bulson. We've got an idea the man is poisoning his uncle in order to get the entire fortune."

"Those books on poison——" began Van Pelt.

"Exactly," said Nelson. "You can testify to them, can't you?"

"To be sure. You had better tell the police of this."

"I shall," said Nelson, quietly but firmly.

The matter was talked over, and our hero determined to call again upon Gertrude, whom he had just left at Mrs. Kennedy's rooms.

When told of the message her uncle had sent the poor girl burst into tears of joy.

"Dear Uncle Mark! He is not as bad as I thought!" she cried. "He would be as kind as ever, if he wasn't so sick. Yes, I will go at once, and I will tell him all."

"And I'll go along—to prove your story and to tell him about the books on poisons," said Nelson.

Soon the pair were on their way to the mansion on Fifth Avenue. Gertrude was all in a tremble, and could scarcely contain herself for joy. The housekeeper let her in, with a smile.

"I am glad to see you back," she said warmly. "I hope you'll stay, Miss Gertrude."

"How is my uncle?"

"Very feeble. I hope the shock doesn't hurt him."

"Is that Gertrude?" came in Mark Horton's voice from the head of the stairs.

Instead of replying the girl ran to meet him, and in another moment uncle and niece were in each other's arms.

"Oh, Uncle Mark!" was all Gertrude could say.

"My dear Gertrude," murmured the feeble man, "I am so thankful you have come back to me! I was cruel, nay crazy—but I will never be so again. Will you forgive me?"

"Willingly, uncle," she answered. "You were not yourself; it was your sickness made you act so. Now I will nurse you back to health and strength."

"Ah! Gertrude! I do not feel as if I can get back my strength again. I am too far gone," murmured the retired merchant.

"Rest yourself, uncle." And she led him to a chair. "After a while I want to have a long talk with you. But tell me first, have you been taking any wine lately—I mean the wine Homer Bulson gave you?"

"A little. But I do not like it—although he almost forces me to take it. Why do you ask?"

"If you will hear me out, I will tell you. It is a long story."

"I will listen to every word, Gertrude."

As briefly as she could she told of what had happened to her since she had left home, how Homer Bulson had followed her up, and what he had done at Lakewood. Then she spoke of Van Pelt and Nelson, and how they could prove that Bulson had purchased several books on poisons. At this last revelation Mark Horton grew deadly pale.

"And you think——" He faltered, and paused. "Oh, Heavens, can it be possible? My own nephew!"

"I would have the wine analyzed," said Gertrude. "And I would have him watched carefully."

At that moment came a ring at the front door bell, and the doctor appeared.

"Ah, Miss Horton!" he said with a smile. "I am glad that you are back."

"Doctor, I want that wine examined without delay," broke in the retired merchant.

"Examined? What for?"

"See if it is pure. I have an idea it is impure."

The doctor smiled, thinking this was another of the sick man's whims. But Gertrude called him aside.

"We think the wine is poisoned," she whispered. "Examine it as soon as you can, and report to me."

"Oh!" The doctor's face became a study. "By Jove, if this is true——" He said no more, but soon departed, taking the wine with him, and also a glass of jelly Bulson had brought in for his uncle's use.

"And so you have brought Nelson with you," said Mark Horton. "Perhaps I had better see him."

"Do you remember him?" asked Gertrude, her face flushing. "He was in the library that night——"

"So that is the young man that was here! Gertrude, for the life of me I cannot understand that affair."

"Nelson did not want to explain all he knew, because he wanted to shield a man who used to care for him, uncle. He thought the man came here to rob you, but he made a mistake, for after he left this house he saw the man come out of the house opposite, with Homer Bulson."

"Who was the man?"

"A rough kind of a fellow who keeps a saloon on the East Side. His name is Samuel Pepper."

"Samuel Pepper? Samuel Pepper?" Mark Horton repeated the name slowly. "That sounds familiar. Pepper? Pepper? Ah!" He drew a breath. "Can it be the same?" he mused.

"Shall I bring Nelson up?"

"Yes, at once."

Soon our hero was ushered into the sick room. He was dressed in his best, and cut far from a mean figure as he stood there, hat in hand.

"You are Nelson?" said Mark Horton slowly.

"Yes, sir."

"I must thank you for all you have done for my niece. I shall not forget it."

"That's all right," said Nelson rather awkwardly. "I'd do a good deal for Gertrude, any day."

"You are a brave boy, Nelson. I believe I once misjudged you."

"You did, sir. I'm no thief."

"I am willing to believe that I was mistaken." Mark Horton paused for a moment. "Gertrude tells me you live with a man named Sam Pepper," he went on slowly.

"I used to live with him, but we parted some time ago. I didn't want anything to do with drink or with a saloon, and I did want to make a man of myself."

"That was very commendable in you. But tell me, is this man's right name Sam Pepper?"

"I hardly think it is, sir. I once saw some letters, and they were addressed to Pepperill Sampson."

"The same! He must be the same!" Mark Horton breathed hard. "Do you know anything about him—where he came from, and so on?"

"Not much. You see, I'm not very old. But he did tell me once that you had been an enemy to my father."

"Me? Who was your father?"

Our hero hung his head and flushed up.

"I don't know, sir."

"This Pepperill Sampson is a villain. Why, he robbed me of my son years ago, to get square with me because I had discharged him for stealing."

"Robbed you of your son?" repeated Nelson. "Do you mean to say he killed your boy?"

"I don't know what he did. At first he was going to let me have my little David back for five thousand dollars, but then he got scared, and disappeared, and that was the last I heard of him or of my child."

"Then David may be alive!" cried Gertrude. "Nelson——" She stopped short. Each person in the room gazed questioningly at the others. Our hero's breath came thick and fast. Then the door bell below rang violently, and Nelson and Gertrude heard Mrs. Kennedy admitted.