"B E good enough to remove your coat," said the old man with a politeness hardly consistent with his fearful purpose.

"Sir," said Oliver, hoping that he might be accessible to reason, "you have no right to experiment upon me without my permission."

"I should prefer your permission," said the old doctor.

"I can't give it," said Oliver hastily.

"My young friend," said the old man, with an air of superior wisdom, "you do not appreciate the important part you are invited to take in the progress of scientific discovery. You will lose your life, to be sure, but what is a single life to the discovery of a great truth! Your name will live for ages in connection with the great principle which I shall have the honor of discovering."

"I would rather live myself," said Oliver bluntly. "Science may be all very well, but I prefer that somebody else should have the privilege of dying to promote it."

"They all say so," said the old man musingly. "No one has the noble courage to sacrifice himself for the truth."

"I shouldn't think they would," retorted Oliver. "Why don't you experiment on yourself?"

"I would willingly, but there are two impediments. I cannot at once be operator and subject. Besides, I am too old. My natural force is abated, while you are young, strong, and vigorous. Oh, yes," and he looked gloatingly at our hero, "you will be a capital subject."

"Look here," said Oliver desperately, "I tell you I won't be a subject."

"Then I must proceed without your permission," said the old doctor calmly. "I have already waited too long. I cannot let this opportunity slip."

"If you kill me you will be hanged!" exclaimed Oliver, the perspiration starting from every pore.

"I will submit cheerfully to an ignominious death, if time is only given me to complete and announce my discovery," said the old man composedly.

Evidently he was in earnest. Poor Oliver did not know what to do. He determined, however, to keep the old man in conversation as long as possible, hoping that help might yet arrive, and the struggle—for he meant to fight for his life—be avoided.

"Did you have this in view when you invited me to dine with you?" he asked.

"Surely I did."

"Why did you select me rather than someone else?"

"Because you are so young and vigorous. You are in the full flush of health."

Now this is a very pleasant assurance in ordinary cases, but under the circumstances Oliver did not enjoy the compliment. A thought struck him.

"You are mistaken," he said. "I am not as well as I look. I have—heart disease."

"I can hardly believe it," said the old man. "Heart disease does not go with such a physique."

"I've got it," said Oliver. "If you want a perfectly healthy subject, you must apply to someone else."

"I will test it," said the old man, approaching. "If you really are subject to disease of the heart, you will not answer my purpose."

"Put down that knife, then," said Oliver.

The doctor put it down. Oliver shuddered while the relentless devotee of science placed his hand over his heart, and waited anxiously his decision.

It came.

"You are mistaken, my young friend," he said. "The movement of your heart is slightly accelerated, but it is in a perfectly healthy state."

"I don't believe you can tell," said Oliver desperately, "just by holding your hand over it a minute."

"Science is unerring, my young friend," said the old man calmly. "But we waste time. Take off your coat and prepare yourself for the operation."

The crisis had come, the old man approached with his dangerous weapon. At this supreme moment Oliver espied a bell-knob. He sprang to it, and rang a peal that echoed through the house, and was distinctly heard even in the chamber where they were standing.

"What did you do that for?" demanded the old man angrily.

"I am not going to stay here to be murdered!" exclaimed Oliver. "I give you warning that I will resist you with all my strength."

"You would foil me, would you?" exclaimed the maniac, now thoroughly excited. "It must not be."

Oliver hurriedly put a chair between himself and the old man.

At that moment steps were heard on the staircase, and someone tried the door.

"Help!" shouted Oliver, encouraged by what he heard.

"What is the matter?" demanded a voice outside. "Father, what are you doing?"

The old man looked disgusted and mortified.

"Go away!" he said querulously.

"Who is there with you?"

"No one."

"It's a lie!" said Oliver, in a loud voice. "I am a boy who has been lured in here by this old man, who wants to murder me."

"Open the door at once, father," said the voice outside sternly.

The old man was apparently overawed and afraid to refuse. He advanced sullenly and turned the key. The door was at once opened from outside.

A man in middle life entered. He took in the situation at a glance.

"You are at your tricks again, sir," he said sternly to the old man. "Put down that knife."

The old man obeyed.

"Don't be harsh, Samuel," he said, in an apologetic tone. "You know that I am working in the interests of science."

"Don't try to impose on me with such nonsense. What were you going to do with that boy?"

"I wished to experiment upon him."

"You were going to murder him, and the law would have exacted the penalty had I not interfered."

"I would have submitted, if I could have only demonstrated the great principle which——"

"The great humbug! Promise me that you will never again attempt any such folly, or I shall be compelled to send you back to the hospital."

"Don't send me there, Samuel!" said the old man, shuddering.

"Then take care you do not make it necessary. Young man, come with me."

It may be imagined that Oliver gladly accepted the invitation.

He followed his guide downstairs, and into the parlor, which was very handsomely furnished.

"What is your name?" enquired the other.

"Oliver Conrad."

"How came you with my father?"

Oliver told the story briefly.

"I am very much mortified at the imposition that has been practised upon you, and alarmed at the thought of what might have happened but for my accidental presence at home. Of course you can see for yourself that my father is insane."

"Yes, sir, I can see it now; but I did not suspect it when we first met."

"I suppose not. In fact, he is not generally insane. He is rather a monomaniac."

"It seems a dangerous kind of monomania."

"You are right; it is. Unless I can control him at home, I must send him back to the hospital. He has been an eminent physician, and until two years ago was in active practice. His delusion is connected with his profession, and is therefore less likely to be cured. I am surprised that you accepted a stranger's invitation to dine."

"I will tell you frankly, sir," said Oliver, "that I am out of employment, and have but forty cents in the world. You could hardly expect me to decline a dinner at Delmonico's under the circumstances."

"To be sure," said the other thoughtfully. "Wait here one minute, please."

He left the room, but returned in less than five minutes. He handed a sealed envelope to Oliver.

"I owe you some reparation for the danger to which you have been exposed. Accept the enclosure, and do me the favor not to mention the events of to-day."

Oliver thanked him and made the promise requested.

When he was in the street he opened the envelope. To his amazement, it proved to contain one hundred dollars in bills!

"Shall I take this!" he asked himself.

Necessity answered for him.

"It is a strange way of earning money," he thought. "I shouldn't like to go through it again. On the whole, however, this is a lucky day. I have had a dinner at Delmonico's, and I have money enough to last me ten weeks at least."