CHAPTER I
A MIDNIGHT EXPEDITION

“Hold on there! Go easy, now, fellows,” cautioned Bart Keene to his two chums, as they stole softly along in the darkness. “What are you making all that racket for, Ned?”

“It wasn’t me; it was Frank.”

“I couldn’t help it,” came from Frank Roscoe in a whisper. “I stumbled on a stone.”

“Well, don’t do it again,” retorted Bart. “First thing you know some one will hear us, and the jig will be up.”

“And then we can’t play the joke on Stumpy,” added Ned Wilding.

“Of course not,” went on Bart. “Easy now. Come on. Keep behind me in a line, and walk in the shadows as much as possible. We’re almost there.”

The three lads bent upon playing a peculiar trick on their chum, Fenn, or “Stumpy” Masterson, kept on toward the Darewell High School, at which they were students. The building set well back from the street, and the campus in front was now flooded with brilliant moonlight. It was close to midnight, and to approach the institution unobserved, to take from it certain objects, and to steal away without having been noticed, was the object of the three conspirators.

“Are you coming?” asked Bart, as he turned around to observe what progress his companions were making. He saw Ned and Frank standing still, crouched in the shadow of a leafless tree. “What’s the matter?” he continued, somewhat anxiously.

“Thought I heard a noise in the building,” whispered Frank, hoarsely.

“You’re dreaming,” retorted Bart. “Come on. It’s getting late, and we want to finish.”

“Yes, and it’s as cold as Greenland,” added Ned. The boys had on light overcoats, for winter was near at hand.

Once more the two advanced, and joined Bart. The three were now in the shadow of one of the wings of the school, and, as far as they knew, had not been seen.

“Which way are you going in?” asked Ned, of Bart, who was leading this midnight expedition.

“Through the side court, and in at the girls’ door. That’s most always open, as Riggs, the janitor, lives on that side of the school, and he doesn’t take the trouble to lock the door, as his house is so near.”

“Good idea,” commented Frank. “Lead on, Falstaff, an’ may he who – ”

“Cut it out,” advised Bart sharply. “This is no time to spout Shakespeare stuff.”

Once more the three advanced. Suddenly Bart stopped, and Ned, who was close behind, collided with him.

“What’s wrong now?” whispered Ned, as soon as he caught his breath.

“Hush!” cautioned Bart. “I saw a man just then! He was right by the front door of the school.” Bart had come to a halt in the shadow of a buttress, just before stepping across an open space that led to the court.

“A man,” murmured Ned. “Probably it was Riggs, the janitor.”

“No, he was too tall for Riggs,” answered Bart. “Besides, he didn’t limp, as Riggs does, from a leg that was once broken. No, this man wasn’t Riggs.”

“What was he doing?” asked Frank.

“Standing near the front door, as if he was going in. Then he seemed to change his mind. I think – There he is again!” exclaimed Bart, suddenly, and he shrank farther back into the dense shadows, his chums following his example.

At the same instant Ned and Frank caught sight of the man. The stranger approached the front door as if afraid of being seen, and, every now and then, he turned about, as the boys could notice to take an observation. As they looked on they saw him suddenly open the front door, after fumbling about the lock, and enter the school, closing the portal behind him.

“Well, what do you think of that?” gasped Bart, after a moment’s pause.

“He’s a burglar!” declared Frank.

“Let’s go tell the police,” suggested Ned.

“No, wait a minute,” advised Bart, putting restraining hands on his two chums. “Don’t tell the police.”

“Why not?” Ned wanted to know.

“Because they might ask what we were doing around the school at night, and we don’t want to tell – do we?”

“That’s so,” agreed Frank. “Maybe that chap isn’t a burglar, after all.”

“You’re right,” came from Ned. “What could a burglar steal in the school?”

“Books, and instruments from the laboratory,” was Bart’s contribution to the opinions. “But I, myself, don’t believe he is a burglar. Possibly he is some one whom Riggs hired to help out with the sweeping and dusting.”

“Let’s wait and see,” suggested Frank, and this was agreed to. Silently the chums, from their place of hiding, kept their eyes on the school. Presently there was a flicker of light in the windows of one of the upper rooms.

“There!” exclaimed Ned, “what did I tell you! He’s a new janitor, sweeping out,” for the light moved to and fro.

“What room is that?” asked Bart.

“Professor Long’s – the place where we’re bound for,” answered Frank.

“Hush! Not so loud,” pleaded Bart. “Some one may hear you, and get on to our trick. I guess you’re right. We’ll wait until he gets out of the way.”

“It may be a long time, and Fenn may come looking for us,” ventured Ned.

“Can’t help it,” decided Bart. “We can’t go in while the man is there.”

There seemed no way out of it, and the three chums crouched in the shadows, waiting. It was cold, and more than once they wished they had not started to play the joke on Fenn, but they were not going to give up now. They saw the light, moving to and fro, but it did not leave the room where they had first observed it – the classroom of Professor Long, the science teacher.

“He must be giving that a good cleaning,” remarked Bart. Hardly had he spoken than the light disappeared. A few minutes later it was visible on the floor below, and then it could be traced, as the person carrying it, descended.

“He’s coming out,” declared Ned.

“So much the better,” commented Frank.

An instant later the front door opened and the man who had gone in, hurried out. He seemed in great haste for, giving a quick look around, he darted away from the school, down the front walk, and up the street.

“Fellows, that was no janitor!” declared Bart. “I believe he was a burglar!”

“But he didn’t have any bundles,” declared Frank. “If he had stolen anything, he’d have to pack it up, as anything of value in the school is quite bulky. I don’t believe he took anything.”

“Then why did he run?” demanded Bart.

This was a poser for his chums, until Frank said:

“It may have been one of the teachers who went back after some papers he forgot.”

“Didn’t look like any of the teachers,” said Bart. “Besides the teachers wouldn’t run, as if the police were after them, and they wouldn’t act as frightened as that man did.”

“Well, what are we going to do about it?” asked Ned. “If we’re going to play that joke, let’s get busy. We won’t say anything about seeing the man unless something developes, and I don’t believe it will. Come on in. The front door seems to be open. We can go in that way, instead of around through the court; less chance of Riggs seeing us.”

“All right,” agreed Bart, “only I wish I knew who that man was.” The time was to come when the boys would have given a great deal to have been able to penetrate the identity of the mysterious stranger. But the three chums gave little heed to that now, for they were intent on playing a joke that Bart had evolved. A little later, finding the front door unlocked, they were inside the school, just as the distant town clock boomed out the hour of midnight.

CHAPTER II
THE MISSING DIAMOND BRACELET

There were three lads who had entered the Darewell High School so mysteriously at midnight, and, had any one seen them, who was acquainted with them, he would have at once asked:

“Where is the fourth member of the quartette? Where is Stumpy Masterson?” For there were four lads in the town of Darewell who were so inseparable that they had come to be known as “The Darewell Chums.” Their names you are already familiar with, and some of my readers have met them before in the previous books of this series.

In the first volume, entitled, “The Heroes of the School,” there was related how the four friends took part in a strange mystery, and how they got at the bottom of it. At one time they went up in a balloon, and were captured by some men who were their enemies, so that, for a time, it looked dubious for the lads. But our heroes were wide-awake, and resourceful, and managed to take care of themselves.

Their home, as I have said, was in the town of Darewell, which was located on the Still River, a stream that flowed into Lake Erie. Living not far from that great body of water, the four chums often made trips to it, though more frequently they went swimming in or sailing on the river, in summer, and skated on it in winter.

In the second volume of the series, called “Ned Wilding’s Disappearance,” a story was told of how Ned tried to become a millionaire on his own account. He speculated in stocks, and to do this he had to go to New York. There he became mixed up in some peculiar transactions, and he thought it was necessary for him to disappear to avoid arrest. His chums, who followed him to the city, tried for some time in vain to find him, and poor Ned suffered many hardships before the affair was finally straightened out.

“Frank Roscoe’s Secret” was the title of the third volume. There always seemed to be a mystery about Frank Roscoe, and his chums could never penetrate it. At times he was moody and distraught, and he seemed to have some secret that worried him. He made no confidant of any one and succeeded in avoiding all inquiries.

The four lads went camping, and it was hoped that Frank would forget his troubles, but, instead, he seemed to get right into the thick of them. Frank, for some years, had believed his father dead, but it transpired that he was not. Mr. Roscoe was kept in a private insane asylum, though he had full possession of his reason, only he was made ill by drugs constantly administered to him by men who had an interest in keeping him out of the way. How he was rescued, and the perils the boys ran in saving him after they had released him from the institution, you will find set down in the third book.

In the fourth book, called “Fenn Masterson’s Discovery,” there was related the details of a long trip the chums took on the Great Lakes. They were aboard a vessel commanded by Captain Wiggs, and almost from the start the boys were involved in a mystery. They were pursued by strange men, when they landed to witness a large grain elevator on fire, and eventually they succeeded in causing the breaking up of a gang of Chinese smugglers, and a band of scoundrels who were secretly taking valuable minerals from a cave, under land owned by a man whom the boys had once befriended. It was not until after some strenuous happenings that these events had come to pass, and, more than once, our friends were in danger. But Fenn Masterson succeeded in getting on the trail of the mystery, through an odd discovery he had made, and, though he was captured by the enemy, he used his eyes and ears to good advantage, so that when his friends came he could lead them to the secret cave.

Following the exciting events of their cruise on the Great Lakes, the boys had returned to Darewell, and had resumed their studies at the High School, where they were great favorites with the other pupils. At the time this story opens the fall term was well under way, and football was the chief sport, our heroes playing on the first team of the school.

The reason for the midnight visit of Bart, Frank and Ned to the school was this: Stumpy, the missing member of the quartette, was an odd sort of lad, always making collections of one thing or another. Sometimes it was postage stamps, or postmarks, and again minerals, or jackknives, or butterflies.

The day of the midnight visit, when the Darewell Chums, together with Bart’s sister Alice (who wanted to be a trained nurse) and her chum, Jennie Smith, were in a drug store getting soda and cream, Fenn had pulled from his pocket, together with his handkerchief, a small mud turtle. There had been a wild scramble on the part of the girls, and some ladies in the store, before Fenn recaptured the reptile.

“What’s that for?” Bart had asked.

“Oh, nothing,” Fenn had answered, as casually as possible.

“It certainly is something,” Ned had insisted, and they had badgered Fenn until he finally admitted that he was now collecting mud turtles, and had a number of them in a pen at home.

This had at once given Bart his cue for playing a joke, and it might be mentioned that the fun-loving youth never let go by a chance to play a trick. A little later, that same afternoon, after Fenn had been sufficiently “rigged” over his new fad, Bart Keene might have been seen whispering cautiously to Ned and Frank.

His proposal was that the three of them should pay a surreptitious visit to the school that Friday night, and, from the room of Professor Long, the science teacher, take a number of turtles, snakes and small alligators which the instructor kept for the use of his class in biology. The three conspirators planned to remove the reptiles, take them to Fenn’s house, slyly put them in with his collection of turtles, and then see what their chum would say when he found his number of reptiles so unexpectedly increased.