She hurried to find out who it was and was relieved to see her husband. She asked him to go to the telephone at once. As the detective listened to Collig, his face grew grave.

"Have you tried the hospitals?-They're not there? -I'll be right down!"

Mr. Hardy had received very disturbing news. Chief Collig had said the boys' roadster had been discovered overturned in a ditch some miles out of Bayport. There had been no sign of either Frank or Joe, and no report of the accident.

"When did you last hear from our boys?" the detective asked his wife. Upon being told, his face clouded. He said he must leave at once to look for them.

"You know something you're not telling me," Mrs. Hardy cried, grabbing her husband's arm as he was about to go out the front door.

"I have a notion their car was stolen. I'm going to drive out to the spot where it was abandoned and see if I can pick up any clues." He was out the door before Mrs. Hardy could make any protest and on his way to Police Headquarters.

Collig was not supposed to be on duty. But when the report of the overturned Hardy car had come in, the Chief had returned to Headquarters. So many mysteries in which the Hardys had been involved 184 had been solved without him that he was not going to let this one slip through his fingers! Furthermore, he secretly admired Frank and Joe and was determined to a.s.sist them.

He went with Mr. Hardy to view the overturned car, which had gone off the road about five miles to the west of Bayport. With flashlights, the two men examined the ground carefully. There was not a a sign of any footprints. sign of any footprints.

"That's strange," the officer grunted. "We haven't had any rain to wash 'em away, either!"

Mr. Hardy did not speak. Slowly he walked back along the road in the direction from which the roadster had come. Reaching a spot about one hundred feet from the car, he played his flashlight over the area and found a set of footprints.

"Here's your answer," he called out. "Pretty daring person."

It was the detective's belief the driver of the car had jumped out and let the roadster go on to wreck itself. Only one person was involved, and that was neither of his sons nor Chet Morton.

"It's a relief to know that," Mr. Hardy concluded, "but it doesn't find the boys. I'm going back to town and start a search."

Collig had his own ideas, so the men separated. Mr. Hardy went at once to 47 Packer Street, and examined the house carefully. Learning that the boys were not there, he drove to various spots which he previously had had under surveillance in connection 185 with the museum thieves. The net result of his investigations was discouraging.

Tired and worried, he returned home at seven o'clock. Refreshing himself with clean clothes and some coffee, he was ready to start out again. Mrs. Hardy and Aunt Gertrude, who had slept only fitfully, asked what he intended to do next.

"I'm going to the Mead house," he said, trying not to show his concern. "I've an idea the boys have found out something and are spying on the place."

He did not tell the two women his real fears. The detective was convinced now that his sons, and probably Chet Morton, were in the hands of the very men he was trying to capture!

CHAPTER XXIII.

Holding a Suspect.

within a half hour after Mr. Hardy had left home, the doorbell rang. Hoping the caller would have good news, Aunt Gertrude dashed to answer it. A man she had never seen before stood there.

"Is this the Hardy house?" he asked, taking off his hat and smiling. Learning that it was, he added, "Are Frank and Joe at home?"

"No," Aunt Gertrude replied.

"When do you expect them?"

"Suppose you tell me your name and why you wish to see them," said Miss Hardy.

"My name is John Mead."

Aunt Gertrude reeled. She put one hand to her forehead and grasped the doorjamb with the other.

"You seem surprised to hear that," the stranger remarked. "Is there something peculiar about it?"

'' I-I-we-thought-you-were-dead!''

The caller laughed. "Me dead? I'm very much alive. What gave you that idea?"

186.

187 By this time Gertrude Hardy had collected her wits. She had heard enough of the mystery her brother and the boys were trying to solve to know that the person who stood before her was one of the suspects in the case. She was hesitant about inviting him into the house; yet she was fearful of letting him go.

As calmly as possible Miss Hardy asked him to come inside. Calling loudly for her sister-in-law, she escorted John Mead into the living room. The boys' mother hurried in.

"Laura, this is Mr. John Mead," Aunt Gertrude announced.

Mrs. Hardy felt faint, but she tried not to show it. The three sat down. It became evident to the caller that the two women were very nervous.

"My coming here seems to have upset you," he said. "A few days ago I met Frank and Joe Hardy on the road. I had trouble with my car and they kindly helped me out."

The two women nodded.

"I recalled having left a light burning in my house, so I gave the boys a key and asked them to go there and turn it off. I just got back to town and I'd like the key."

He stopped speaking, expecting one or the other of the women to say something, but both remained silent. They were staring at a ring he wore on his finger. This was the first time they had seen the strange open-faced Y. Suddenly Mrs. Hardy real188 ized that the awkward pause had been rather long.

"Oh-ah-yes," she said. "I believe the boys did have a key; but they are not at home now and I don't know where it is."

"You don't mean they've lost it?" Mr. Mead asked quickly.

"Oh, no," the two women replied together.

Aunt Gertrude again brought up the subject of how they had heard that John Mead, who owned the house on the bay, had died five years before.

"I see what you mean," the caller smiled. "He was my uncle."

"Your uncle!" Mrs. Hardy cried. "We thought he had no relatives."

"I guess everyone thought that," John Mead went on. "To tell you the truth, my uncle was a rather eccentric man and people knew little about him. He was not married, and my father and I were his only living relatives. We lived in England most of our lives.

"A few years ago I received a strange note from my uncle. He wrote that he was sending me a box and would explain its contents later. He wanted me to be sure of receiving the gifts before telling me what they were."

John Mead explained that the box contained the ring he wore and some odd-looking keys; that was all. He had written to his uncle at the Bayport address saying the package had come, but he had never received a reply.

189 "Apparently Uncle John died just at that time, but I didn't know this. It seems no will was found, but my father once told me my wealthy relative was leaving everything to me. Recently I arrived in this country and came here to Bayport thinking I'd see my uncle.

"During my inquiries about his death I heard of Mr. Hardy and his sons, and how clever they are. When I actually met your boys on the road, I thought it would interest them to go out to the house and find out how to get in."

Though the stranger seemed nice enough, the two Hardy women were suspicious of him. Aunt Gertrude quietly left the room, went upstairs, and telephoned to Police Headquarters. Chief Collig, still out on a personal hunt for Frank and Joe, was not available, but the sergeant on duty promised to send a plain-clothes man over at once.

During Aunt Gertrude's absence from the living room, Mrs. Hardy mentioned the light Mr. Mead had said he left burning in the house, and asked what kind it was.

"An electric lamp," the man replied.

"I should have thought the power company would have shut off the current," she said, looking at the caller intently.

"No doubt they did," John Mead replied. "But my uncle had an auxiliary system of his own."

This explanation seemed plausible enough; yet the detective's wife found it hard to believe that it 190 could still be in running order after five years of disuse.

A few minutes later the doorbell rang. Aunt Gertrude hurried to the hall to admit the plain-clothes man. Quickly she whispered her suspicions to him, then brought him into the living room. She introduced the policeman as a friend.

"I must be going," John Mead said quickly. "I'll come back another time for the key."

"How will you get into your house?" Aunt Gertrude asked him bluntly.

The caller explained he had a key to the back door of the mansion. As he started to leave, the plain-clothes man blocked the doorway.

"I'd like to ask you a few questions," he said.

For several minutes the detective quizzed the stranger, but learned nothing from him other than what he had told the two women. Finally John Mead became irritated.

"You'd think I'm some sort of criminal!" he burst out. "I know this is a detective's home, and you probably think everybody who comes here is a suspect of some kind, but I can't see why I warrant such treatment!"

"Well, if you must know, you are are a suspect," Gertrude Hardy burst out. a suspect," Gertrude Hardy burst out.

John Mead looked as if someone had struck him. He recovered himself in a moment, however, and demanded to know what she meant. Mrs. Hardy suggested they all sit down.

191 "This man is a policeman," Aunt Gertrude explained. "And if you try any funny work, Mr.

Mead, he'll arrest you!"

"I a.s.sure you I'll not try any funny work," John Mead said, his eyes blazing angrily, "but I insist upon knowing why you are virtually holding me a prisoner."

"That ring you are wearing was stolen from a museum!" Miss Hardy cried excitedly.

"How do we know you didn't steal it yourself?"

John Mead turned pale. Nervously he insisted he was not a thief, and that he had received the ring by mail from his uncle.

"Your story sounds on the level," the plain-clothes man spoke up. "But if you're going out to the Mead house I'm coming along."

"And we are too!" chorused the women.

They thought it best not to mention the fact that Mr. Hardy was out there searching for the boys. Moreover, they were so worried about Frank and Joe they wanted to be on hand in case of trouble.

The plain-clothes man drove the four in a police car. Reaching the Mead house, they found Mr. Hardy and two of his men still trying to get into the mansion. The detective was surprised to see his wife and sister, and even more so to meet John Mead. He scrutinized the man closely and decided at once his story was true; if he was involved with any crooks, it was not to his knowledge.

"I'm very glad you came," the detective said. "I 192 have reason to believe there's trouble inside the house, and I was just about to break in.

You have a key?"

"Yes, to the back door."

Mr. Mead led the way toward the bay side of the house, found the secret keyhole, and opened the door. He remarked that he had spent many hours at the place before discovering how to get in.

The man clicked a wall switch, and the lights in the kitchen came on. He told Mr. Hardy of the secondary electric system in the house.

"That explains one of the mysteries," the detective said. "My boy Frank received a bad shock and we could not understand what made the current go off and on. I feel sure someone has been tampering with the system."

Mr. Hardy and his two men, after searching the house thoroughly, returned to report they had not found the boys.

"You may as well go home," Mr. Hardy told his wife and sister. "Thomas here," he added, referring to the plain-clothes man, "will take you back. I'd like Mr. Mead to stay."

After their departure, Mr. Hardy gave John Mead a sketchy account of the mystery on which he was working. He revealed the part Lenny Stryker had played in it, and how the only clue to his whereabouts lay in the secret panel.

"Trails lead to this house," he said.

John Mead was dumfounded. He had no idea 193 the house contained anything of a secret nature other than the peculiar doors and windows, but he could well imagine his eccentric relative might have built in a hidden room.

"Uncle John was very inventive, my father told me. Perhaps he had a secret place where he worked. But I never heard of one."

Mr. Hardy was sure John Mead was telling the truth. Nevertheless, he signaled to one of his men to keep close watch of the fellow; not only to see that he did not escape, but to watch him and see if his actions gave a hint that he knew more about the secrets of the mansion than he had admitted.

Mr. Hardy and the other detective went outside and surveyed the house carefully. They decided that architecturally the most likely place to build a secret room would be off the library. They went inside and began a careful examination of the carved paneling in that room.

The boys' father astutely focused his attention on the fireplace, and it was not long before he located the telltale oak tree with its movable leaf. He realized at once that the only way to move the disk would be with a magnet of considerable power. Hoping that one was hidden in the room, he cast his eyes about the place.

At this instant the keen ears of the plain-clothes man near the hall door detected a slight sound. Instantly he made a hissing noise to put the others on their guard. Extinguishing their flashlights, the 194 three detectives melted into the shadows of the furniture, one of them pulling John Mead with him.

The front door opened and closed again. Footsteps came along the hall. Finally a figure came stealthily into the library and walked directly to the fireplace. The four men watched intently.

Was the intruder going to open the secret panel?

CHAPTER XXIV.

The Capture.