At his first opportunity to get away from recitations the following day Frank took Diamond and Rattleton and hastened down to the stable to find out how Nemo was coming along.

Grody, who had just saddled a horse for a gentleman, met Frank, and the expression on his face was anything but reassuring.

"Well, how is the pony this morning?" asked Merriwell, anxiously.

"Just as lame as he were, sir," answered Grody. "I've been tryin' to find out what it were that happened to him, but I can't, sir."

"Did you take him to the shoer the first thing this morning and have his feet examined, as I directed?"

"I did that, sir."

"And what did the shoer say?"

"He located the lameness in the same foot what we said were lame, sir, and he took off the shoe, but he said as how it were all right, and no fault of the shoeing. He didn't know but a nail might have gone too deep, sir, but he found that were not it."

This was anything but satisfactory, and Frank showed it by his face.

"Well," he said, "you know I told you to summon Dr. Cobb, if it proved something beyond the shoeing."

"And that were what I done, sir."

"And the doctor could not tell what ailed the horse?"

"The doctor has not come yet, sir. He were busy when I send the message to him, but he said—— Here he is now, sir."

A rig drew up at the door, and a short, stubbed, red-bearded man stepped out. This man entered the stable with a quick step and called to the hostler:

"Well, Grody, did you telephone me?"

"Yes, sir, I did, sir," said the hostler, quickly.

"Important case, you said?"

"Yes, sir, very important."

"Where's the horse?"

"I'll bring him right out, sir."

The hostler hastened to do so, and Dr. Cobb looked keenly at Nemo.

"Walk him around," directed the doctor.

Grody obeyed.

"Just a bit lame," commented the doctor. "It may be a slight strain. It doesn't seem to be much."

"But it grows worse when he is taken out on the road," said Frank. "It was very bad yesterday afternoon."

The doctor glanced at the boy.

"Your horse?" he asked.

"Yes, sir."

"When did you first notice he was lame?"

"Yesterday afternoon."

"Had him out this morning?"

"Grody took him to the shoer, that's all."

"What did he say?"

"Said there was nothing the matter with the way Nemo is shod."

"Perhaps he lied. Didn't want to hurt his business. Did he do anything?"

"Yes, he reset the shoe on the lame foot."

"Hum! Horse may be all right by to-morrow or next day."

"I do not think he will, doctor."

"Eh? Why not?"

"Because I have reasons to believe he was made to go lame."

"Is that so? Well, now the matter becomes more interesting. What causes you to think anything of the sort?"

Frank explained, and the doctor listened attentively to his story.

"This is worth investigating," he declared. "I know a few of the tricks of these fellows, and I think I'll find out what was done to your horse, if anything was done."

The boys watched the doctor with great interest. They saw him examine the lame leg from the knee down. In doing this he put on a pair of spectacles.

Nemo was nervous. He seemed afraid the doctor would hurt him, and it was not found easy to make him stand.

At last Dr. Cobb uttered a sharp exclamation.

"Bring my case, which you will find under the seat in my carriage, Grody," he directed.

Grody hastened to obey.

"Have you found out what the matter is, doctor?" Frank anxiously asked.

"I believe so, but I am not sure yet."

Jack and Harry came near, eager to learn what had been done to lame the horse.

The doctor opened his case, and took out some tweezers.

"Do you see this hair here?" he asked, having brushed the fetlock aside and taken the end of a hair in his fingers.

The boys saw it, but wondered what that hair could have to do with the lameness of the horse.

"It is not the right color," declared the doctor. "You see it is white, instead of being the color of the other hairs here."

Despite himself Frank felt his anger rising. How could the color of a hair make the horse lame? Did the man take him for a fool because he was a boy?

The three boys exchanged glances, and Harry made a threatening gesture at the back of the doctor's head.

"I see the hair is white, sir," said Frank, his voice cold and hard; "but I scarcely think a white hair could make my horse go lame. I know I am a boy, but I do not like to be taken for a fool."

The doctor looked up and saw the indignation expressed on the faces of the three lads. Then he chuckled in a singular way and said:

"Wait till I get through, young man. I do not take you for a fool ordinarily, but you can easily make a fool of yourself over this matter."

He had taken the short white hair, which was very coarse, in his fingers, having separated it from the others.

"Notice the peculiar place where this hair seems to grow," he directed. "It is not a part of the fetlock, but the fetlock hid it from view. I am going to pull this hair out, but first I want you to notice that there is another hair, it seems, on the other side of the ankle, and it is just like this. See it?"

The boys saw it.

"In a moment you won't see it," declared the doctor, as he adjusted the tweezers, getting a careful grip on the end of the hair. "Here it comes."

Then he quickly drew it out and Nemo started a bit, but was quieted by Grody.

"Young man," said the doctor, "look at this. This hair appeared to be about an inch in length, but now it is three inches long. It is not broken off, and yet it has no root. I will guarantee there is not another hair on this horse like it! I will guarantee it did not grow on this horse! I will guarantee it was what made this horse lame! And I do not want my fee if this horse shows any lameness two hours from now!"

The boys were astonished, as their faces indicated.

"But, doctor, I do not understand!" cried Frank. "You must explain. How could a hair——"

"I will explain. It's an old trick, but one seldom tried. This hair came from the tail of a white horse. It was threaded into a long, keen needle. The fellow who got at your horse yesterday was an expert. With one jab of that needle he passed the hair through the flesh just back of this cord. It went in at one side, and came out on the other. After that, while he was pretending to look at the horse's feet, he clipped off the ends, and the hair was left in there. It could remain a day or so without doing any particular injury, but it was bound to make the horse lame as soon as he used that leg much. If it had been left there permanently it might have ruined the horse. That is all, young man."

"Why was a white hair chosen, doctor?"

"The fellow felt sure it would not be noticed, and yet he could quickly locate it by its color when the time came for him to cure your horse of its lameness."

Once more the boys looked at each other, and this time it was plain they realized there were some things they did not know.

"Doctor," said Frank, promptly, "I wish to beg your pardon. I believe I said something rather hastily, but now I wish to say that you know your business thoroughly."

The doctor smiled, and closed his case.

"I have been in the business all my life," he said, "but I expect to continue to learn something new about it as long as I live. I will say that I doubt if I should have seen what was the matter with your horse if you had not told me of the fellow you believed had lamed him and how the horse kicked up a racket when the man was in the stall. That set me to looking for tricks, and I found the hair."

Frank offered to pay the doctor, but he refused to take it then, saying:

"Here's my card, young man. If your horse is all right this afternoon you may send me five dollars. You may need me again some time."

Then he strode out of the stable, flung the case under the seat, scrambled into his carriage, caught up the reins, and away he went in a hurry.

"Well, may I be farred and tethered—I mean tarred and feathered!" cried Harry Rattleton. "I never saw anything like that before."

"Nor I," confessed Jack Diamond. "It's astonishing! I have learned something to-day that I never knew before. I never would have dreamed that a hair could lame a horse in that way!"

"You want to look out for Nemo now," said Harry, "and not let that chap get at him again."

"I mean to," asserted Frank. "I have sent for my colored boy, Toots, to come on and keep watch here when Grody is unable to do so. Till he gets here, Grody, I want you to watch Nemo like a hawk. I hardly think the whelp will try another trick, but there is no telling. I gave him a bad thumping."

"But not half what he deserved!" cried Diamond.