She must be buried!"

The old man began raking furiously at the pile of plaster that blocked the corridor. At that mo- ment Nancy was lying stunned on the floor of a closet some distance from where her friends were working. The force of the explosion had hurled her into the large storage closet, then the door had slammed shut. The corridor ceiling had fallen, sealing off the entrance to the closet.

When she regained consciousness Nancy found herself in total darkness and wondered where she was. Slowly the dazed girl got to her feet and felt around her prison. At last she found a door and tried it. It would not budge, and there was no other exit.

"What'll I do?" she thought. "And where is George?"

Suddenly Nancy heard her name being called.

With all her strength she pushed against the door. It yielded slightly. Through the crack she shouted, "George!"

"Nancy! Where are you?" came a m.u.f.fled reply.

"Here! In the closet!"

Salty and George leaped across the rubble.

With the rake and their hands and feet they cleared away enough of the debris to free Nancy.

As she squeezed outside, Salty mumbled: "Thank goodness you're alive!"

George embraced her friend in excited relief.

"You feel all right?"

"I think so. What caused the explosion?"

Suddenly Nancy recalled the two men who had run from the building. "What became of those men who were in here? Did you see them, Salty?"

The clam digger shook his head. "I saw no one."

Nancy, George, and Salty plunged through the marsh gra.s.s toward the riverbank. The damaged motorboat was no longer there.

"Those rascals sneaked away, drat 'em!" Salty muttered in disgust. "Do you think that makes 'em guilty, Nancy?"

"Guilty on two counts," the girl replied.

"Guilty of damaging the boat I rented, and most likely, guilty of causing the explosion."

"But why set off an explosion?" George asked.

Nancy shrugged. She did not want to mention any of her theories just yet, but it occurred to her that Daniel Hector may have been covering up some incriminating evidence against himself. Mrs.

Fenimore had vehemently declared that she did not trust the lawyer.

During the trip back to Salty's dock, the clam digger and the girls kept their eyes open for the blue-and-white motorboat. But they did not see it.

"I'll be glad to take ye on a trip again," the amiable man offered when they reached River Heights.

Nancy thanked him. On the way home she was thoughtful, and could hardly wait for the moment when she could talk to her father. In his den after dinner she told about Daniel Hector's apparent connection with the explosion at the Heath but- ton factory.

"But why would Hector want to damage prop- erty he's obligated to look after?" Mr. Drew asked.

"It doesn't make sense."

"I'm sure there's a great deal more to the Heath case than Juliana's disappearance," Nancy de- clared. "The explosion today, for example. There may be something pretty sinister in back of it all."

"I agree with you," Mr. Drew said soberly.

"Nancy, I know it's useless to ask you to give up trying to solve a mystery-"

"Oh, it is, Dad!"

"At least I can ask you to be careful. Remem- ber, you're my one and only daughter."

"I'll keep it in mind," she said, hugging him affectionately. "Now, about the Heath affair. Isn't it possible that Hector has been investigating the property himself, hoping to discover the due Walter Heath mentioned in his will?"

"You mean the one by which Juliana can iden- tify herself beyond all doubt?"

"Yes, Dad. If a dishonest person stumbled upon that clue, it might be possible for him to have an impostor claim the fortune."

"That wouldn't be so easy, Nancy. A number of persons knew Juliana."

"But," Nancy countered, "if she has been through a terrible experience of some kind, she could have changed so much even her own sister wouldn't recognize her."

"True. I follow your reasoning. Nevertheless, any woman who put in a claim would have to satisfy the court that it was a just one."

Nancy glanced steadily at her father. "Do you think Mr. Hector has really tried to find Juliana?

If he isn't honest-"

"Nancy, I don't like to think the man would be involved in anything underhanded. I don't ap- prove of his methods in handling law cases, but there is no proof that he has actually done any- thing dishonest."

"But you admit," Nancy said, "that the Heath case looks suspicious?"

"Yes, I do, Nancy."

His daughter went on, "I've even thought that maybe Juliana is being held a prisoner some- where."

Mr. Drew looked surprised. "In the castle?"

"Who knows?" Nancy replied. "Dad, I can't decide where to begin looking for her. The ex- plosion today kind of changed my plans."

"In what way?"

"I heard that Walter Heath made scientific ex- periments at his estate. If Mr. Hector suspects there's a secret within those crumbling walls-"

Mr. Drew gazed at Nancy. "Young lady, you're leading up to something!" he declared with a twinkle in his eye. "Out with it!"

"I'm only trying to arouse your curiosity,"

Nancy confessed with a laugh. "Why not go to the factory with me? You may find a clue I over- looked. I need your help. Dad."

"Well, if you put it that way," her father said, "Actually, I haven't the time to spare, but I'll go to please you."

"Tomorrow morning then."

"So soon?"

"Dad, don't forget, I must solve this mystery in three weeks!"

CHAPTER VII.

A Puzzling Message.

Nancy and her father were up early the next morning. They hastily made breakfast before Hannah came downstairs, then drove to the lane Mr. Drew knew led to the damaged b.u.t.ton fac- tory. The road was in very bad condition, and there was no gate.

"I see why those men came by boat," said Mr.

Drew, stopping the car some distance from the building. "We'll walk from here."

Nancy led the way through the dew-laden gra.s.s to the scene of the explosion. There was no sign of anyone near the factory.

"The explosion did a good job of destruction,"

the lawyer commented as the Drews cautiously en- tered the building.

"Here's where the wall caved in between George and me," Nancy explained.

"Looks as if it might have been dynamited,"

her father remarked. "Let's see if we can find any evidence."

For the next half hour father and daughter scrambled among the rubble. When they discov- ered nothing of importance in the corridor, they decided to investigate the large workroom at the rear. It was necessary to go outside and climb in through a window to reach the room, because the inside entrance was blocked.

"Oh, it's like a ghost town," Nancy said as she surveyed the rusted machinery covered with lay- ers of dust. "To think that this once was a pros- perous factory, Dad." She pointed. "What was this machine used for?"

"Cutting," her father explained. "The mollusk sh.e.l.l is placed inside. An operator moves a lever and down comes the circular steel saw. Presto! A little sh.e.l.l disk drops into the hopper. Another machine slices the disk into pieces of uniform thickness and there you have some pearl but- tons!"

"How clever!" said Nancy.

"The b.u.t.tons pa.s.s through still another ma- chine which polishes them," Mr. Drew went on.

"In the last operation thread holes are drilled through them."

"Dad! Look!" Nancy cried suddenly.

A sc.r.a.p of torn paper was sticking from a comer of the rubble in the doorway. Near it, in a thick layer of dust, were several footprints.

Nancy picked up the paper which had part of a message on it. The writing was bold and read: Dear C, Some cret which I in a wall famous worthy "Interesting," Mr. Drew commented, scanning the paper. "But I can't say that it makes much sense. The footprints might be a better clue."

He stooped to examine them. "Freshly made, no doubt," he said. "Perhaps the two men have visited here since the explosion."

"If so, it proves they're searching for some- thing they think was hidden and could be found only by blasting it out."

"Not necessarily. The explosion could have been an accident, or was set off for some other purpose and may have nothing to do with Juli- ana's inheritance," Mr. Drew remarked.

Nancy was staring at the torn note. "I believe I've stumbled upon a worthwhile clue just the same. I'm sure the partially missing word is se- cret"

She pocketed the message and reluctantly left the factory with her father. At home, later on, Nancy spent more than an hour trying to figure out the missing words of the note. Who had written them? The paper appeared old, the ink slightly faded.

"It wouldn't surprise me if Walter Heath had written this," she told Hannah Gruen.

"I know how you might find out!" the house- keeper said.

"How?"

"Walter Heath was a member of the River Heights Historical Society before his death. I'm sure the society has specimens of his handwrit- ing."

"Hannah, you're a genius!" Nancy cried, giv- ing the woman a hug. "I'm off to the Historical Society this very minute!"

Luck was with the young detective. On labels, books, and pieces of furniture which Walter Heath had given to the organization's museum she found several samples of the deceased estate owner's handwriting.

"It's the same as that in the note!" Nancy ob- served excitedly. "Now, if only I can find the miss- ing part of the message 1 But Daniel Hector may have the rest!"

Nancy decided to seek her father's aid once more and asked him to talk to the lawyer about the Heath case. Carson Drew did, and then re- ported to his daughter. "Hector certainly was reluctant to discuss the case."

"Didn't he tell you anything?" Nancy asked.

"Nothing worth mentioning. As soon as I spoke of Heath Castle and the b.u.t.ton factory, he dosed up as tight as Salty's clams!"

"Did you mention Juliana's name?"

"Yes. Mr. Hector stressed that he was still searching for her."

The Heath Castle mystery was no nearer a solu- tion than before. Eager as Nancy was to revisit the estate that afternoon, she found it impossible.

Her father had made her promise not to go there alone. Neither Bess nor George was free to ac- company her until the next day.

The next day, after Sunday church services, the three girls set out in Nancy's car, carrying a picnic lunch. On the way Nancy explained the latest developments in the mystery. She added, "Nothing must drive us away from the castle grounds until we've investigated every nook and corner!"

Soon the familiar ivy-covered front boundary wall loomed ahead. Nancy parked beneath a cool tunnel of overhanging trees. The car was well hidden.