He told them that the boys had found nothing at the farmhouse to connect Crosson with the place and had not been disturbed during the night.

George was unwilling to accept this statement without an explanation. "When did the clothes vanish from the chute?" she asked.

Burt and Dave looked blank. They admitted they had failed to look in the chute and had no idea when the clothes might have been taken out.

"But I'm sure it wasn't after we arrived," Burt declared. "Someone must have removed them between the time Bess and Dave were there and we guys went back to the farmhouse."

On their return trip to Emerson, Bess and George continued to tease Dave and Burt. They accused them of sleeping so soundly that they did not hear the man, and worst of all of snoring so loudly that the man knew the boys were there.

"Enough! Enough!" Dave cried out, putting his hands over his ears. "I have to concentrate now on my next cla.s.s." He looked at his watch. "Burt," he said, "you'd better speed up or we'll both be late."

Nearing the campus, Nancy told the boys about the mysterious phone call asking where they were. "I wonder if it was before or after the caller visited the farmhouse."

Burt and Dave felt sure it was before. "On the other hand, if he came there after we arrived, he probably didn't realize we were there," Burt added. "We don't snore!"

He drove directly to the cla.s.sroom building and the boys got out. Nancy took the wheel and headed for the fraternity house. A student was on duty in the front hall.

"Any word about Ned yet?" Nancy asked him.

"Nothing," he answered. "But say, there's been some more excitement on the campus. A burglary!"

"Really?" George spoke up. "Where?"

"Over in the office and lab where the electronic and computer work is done. Ned and Mr. Crosson experimented there. Lots of things were taken."

At once Nancy, Bess, and George wanted to know the full story of the theft. They jumped into the convertible and Nancy sped to the scene. Could there be any connection between the burglary and the mysterious disappearance of Crosson and Ned? Nancy wondered.

CHAPTER VII.

The Explosion

WHEN Nancy, Bess, and George reached the laboratory, they found the entrance door wide open. Professor t.i.tus, who was in charge of the department, and a policeman were at work hunting for clues to the burglar's ident.i.ty. The officer was taking pictures of fingerprints.

Nancy introduced herself and her friends and told the professor that they were trying to solve the mystery of Ned Nickerson"s strange disappearance.

"Oh yes," t.i.tus said, "and I understand you are being very thorough. No doubt that is why you are here."

"We've been away on a sleuthing mission and just got back," Nancy explained. "When we learned what had happened here, we came right over."

Professor t.i.tus took the girls to meet the fingerprint expert, who by this time had developed all his pictures from the fast-processing film.

He remarked, "These very faint old ones and the newly made group are the same."

"Does that mean," Nancy asked, "that the person responsible for the theft is well acquainted with this lab?"

The officer was inclined to think so. "I'll see if the college has the fingerprints of everyone using this laboratory."

Professor t.i.tus spoke up. "That has never been required," he said. "I am afraid you'll have to look elsewhere for identification."

Nancy was sorry to hear this. She wanted to mention Crosson's name because in her own mind she felt sure that he had burglarized the lab. But on the other hand, why would he rob the place when he could work there? She decided to say nothing yet to the police.

"Perhaps Crosson has gone away for good," the young detective said to herself.

She asked Professor t.i.tus if it would be all right for her to look around.

"Yes, indeed," he said.

The three girls walked about slowly, examining the long worktables, some with sinks, others with electric outlets. Against one wall were computers of various sizes. The electronic equipment seemed complicated.

"This place is like a maze," she thought.

Idly Nancy wandered over to a metal file cabinet which stood by itself on one side of the room. "I think I'll just peek inside. Maybe I can pick up some information to help solve this case."

She pulled open the top drawer and found it filled with books. They were of a technical and specialized nature and Nancy doubted that they would lend a clue.

"I'll look at them later," she decided, closing the drawer.

Next she drew out the large second drawer. Before Nancy had a chance to find out what it contained, there was a sudden explosion inside the drawer. It tore the file cabinet apart.

The force knocked Nancy against the opposite wall, but fortunately she was not hit by any of the flying debris. The others in the room rushed over to see if she was all right.

"Nancy!" Bess cried out.

"I'm okay," the stunned girl answered shakily. "I must have triggered off a bomb."

As George glanced toward the wreck, she yelled, "Fire! The papers are on fire!"

Professor t.i.tus had rushed to a nearby extinguisher and told the others to get another from the outer office. The flaming papers crackled and sent up greenish smoke. The two extinguishers failed to douse the flames.

"Notify the fire department!" Professor t.i.tus shouted, and George dashed to the office phone to put in the call.

The odor from the burning contents of the cabinet became intolerable. Everyone was forced to leave and the door was closed. Professor t.i.tus suddenly recalled that there was a manual sprinkler system in the ceiling of the lab. He turned two metal wheels on the wall, then opened the lab door a crack and peered in. Water was streaming down. By the time the firemen arrived, the blaze had been extinguished.

"I guess our equipment isn't needed," said one of the men with a smile, "but we'll investigate the cause of the fire."

Professor t.i.tus looked a little sheepish. "I only remembered about the overhead sprinkler system after we called you," he said. "What I think we do need here is an inspection by the police bomb squad." He told about the explosion in the file cabinet, and the fire captain in charge telephoned at once to the head of the bomb squad.

Nancy remarked to the other girls, "If there was anything important in the file, it's no good to us now."

George replied, "I guess that's the way the burglar planned it."

Nancy turned to Professor t.i.tus. "Please tell me all you know about Zapp Crosson."

"Actually I know very little," he replied. "Why? Do you-?" When the young detective did not offer to explain her interest in the graduate student, Professor t.i.tus went on, "The young man was secretive and uncommunicative. Several times I tried to engage him in conversation, but all he ever told me was that his parents were foreign and he had had part of his education in Europe."

Nancy said she understood that Crosson worked next to Ned in the lab.