At the Hardy home they found Fenton Hardy awaiting them. Mrs. Hardy seemed anxious and frightened, particularly when she saw Chief Collig, but her husband managed to allay her fears.
“It’s all a bad mistake, Laura,” he assured her. “The boys have done nothing wrong. We’ll go into the matter thoroughly and see where the trouble lies.”
He ushered Chief Collig and his sons into the study, then closed the door.
“Well, Chief,” said the great detective easily, “this seems to be a bad mix-up. I didn’t meet the boys when they arrived this morning because I knew you wanted to have a talk with them and I didn’t wish to interfere. How do things stand now?”
“They’re under arrest,” returned Collig. “They wanted me to bring them home so they could see you, and I consented.”
“Under arrest, are they? Well, that’s bad. I thought they would be able to prove an alibi.”
“They can’t,” said the chief. “It isn’t my doing, Mr. Hardy. The post office people took out this warrant and if I didn’t arrest them, somebody else would.”
“I quite understand that, Chief.” Mr. Hardy turned to his sons. “Well, boys, this looks pretty bad. What have you to say?”
“It’s a big surprise to us, Dad,” said Frank. “The first we heard of the robbery was over the telephone this morning. We don’t know anything more about it than that. I think you know well enough that we’re innocent.”
Mr. Hardy nodded. “I’m quite sure of that. The fact is, however, that there is some damaging evidence against you. It will have to be explained. When were you at the airport last?”
“We’ve never been at the airport, Dad.”
“You’ve never been there at any time?”
“No,” said Frank. “We started out to visit the airport one day, but that was the time Giles Ducroy’s plane crashed when we were still some distance away. We turned back and returned to town.”
“Where were you yesterday afternoon?”
“We took the car and went for a drive out the Shore Road, to Beach Grove.”
“Did anyone see you? Can anyone prove it?” inquired Mr. Hardy, eagerly.
Frank shook his head. “No one saw us, so far as I know. You’ll just have to take our word for it.”
“That’s quite enough for me,” admitted Mr. Hardy. “But the police require something more substantial than that.”
“What’s all this about clues?” demanded Joe. “Chief Collig says they found some clues at the airport that seemed to connect us with the robbery. What were they?”
“We found a sweater, for one thing,” declared Chief Collig. “It was a blue sweater, with white trimmings.”
“I had a blue sweater with white trimmings,” said Frank promptly.
“Where is it now?” asked the chief.
“I lost it.”
Chief Collig nodded grimly. “You lost it at the airport. That’s where it was found.”
“My sweater? Found at the airport?” exclaimed Frank, dumbfounded.
“There are plenty of blue sweaters like Frank’s,” scoffed Joe. “How do you know it was his?”
“Because,” returned the chief, “his name was in it. It was on a tag inside the collar.”
Frank was silent for a moment. He realized how damaging the discovery of the sweater might be.
“I did have a tag with my name on it, stitched inside the collar of my sweater,” he admitted. “I guess it must be mine, all right. But I didn’t leave it there. I lost the sweater more than a week ago. I left it out in the barn one night and I haven’t seen it since.”
“Well,” said Chief Collig, “the sweater has been found. It was lying in the airport, in a place where you—where the thieves lay in hiding until the mail bags were left unguarded.”
“Anyone could have put the sweater there,” declared Mr. Hardy. “The person who took Frank’s sweater from the barn could have done that.”
“We have more evidence than that,” insisted the chief. He turned to Joe. “Let me see the soles of your shoes?”
Mystified, Joe elevated his feet. The chief looked at the soles, then referred to a paper which he removed from his pocket.
“You’ll find it hard to explain that,” he said, and placed the paper on Fenton Hardy’s desk.
Joe’s shoes had been bought at an exclusive sporting goods store in Bayport just a few days previously. They were new, and of an original design, the rubber soles were stamped in a peculiar manner. Probably no more than a few pairs had been sold since the shipment arrived.
The paper which Chief Collig produced had a penciled drawing which corresponded to the stamped design on the soles of Joe’s shoes.
“That drawing,” explained the chief, “was made from the footprints found at the scene of the robbery. What size of shoe do you wear?”
“Size six,” returned Joe.
“These footprints were made by a size six shoe. I went to the shoe dealers in town and I found that only one merchant handles shoes of that type. He says they are a new kind of shoe and that he has sold only one pair of sixes since they arrived. And he sold that pair to you. How do you explain that?”
“I didn’t leave the footprints there,” insisted Joe doggedly. “Someone else must have a pair of those shoes, same size as mine.”
“You are wearing the only pair of those shoes ever sold in Bayport,” declared Chief Collig. “The footprints were found at the airport in the mud. And there’s something else.” He took an object from his pocket and held it out in the palm of his hand. “Do you recognize that?”
“My knife!” exclaimed Frank.
“You admit it, eh?” The chief grunted with satisfaction. “You see the initials on it. J. H. to F. H.?”
“Joe gave it to me for Christmas, and he had the initials engraved on it.”
“I suppose,” sneered the chief, “you lost the knife at the same time you lost your sweater?”
“To tell the truth, I did.”
Fenton Hardy was pale and distressed.
“This looks
