The boy from the country had suddenly lost interest in clearing up the mystery surrounding Shadow Hamilton, and allowed the others to finish the search for class pins and postage stamps. One more pin was found and three rare stamps from Brazil, and then the search was abandoned, and they returned to Oak Hall, Dave carrying the sailor's possessions.
That evening there was an interesting interview in Doctor Clay's office, in which Dave and his friends took an active part. The worthy master of Oak Hall listened to all the boys had to tell with keen attention, and smiled quietly when told how Dave and Roger had first followed Shadow in his somnambulistic feat. He took possession of the class pins and the stamps, and said the latter were undoubtedly from his collection.
"We now have nearly all of the class pins," he said. "But fully nine-tenths of the postage stamps are still missing and they represent a value of at least twenty-five hundred dollars. I am tolerably sure that Maurice Hamilton took them in his sleep, but the question is, did he destroy the others, or did somebody else come along and take them?"
"I believe Chip Macklin came to see you, sir," said Dave, significantly.
"He did, Porter, and I am going to follow that clew up—if it is a clew," answered Doctor Clay, gravely.
After the others had departed, Dave showed the things he had found belonging to Billy Dill. The master of the Hall was as much astonished as anybody over the resemblance between his pupil and the photograph, and examined the picture with care.
"I do not wonder that you wish to investigate this," said he. "I should wish to do so, were I in your position."
"I have simply got to do it, Doctor!" cried Dave. "I shall not be able to settle my mind on a thing until it's done. Would you go home and see Mr. Wadsworth and Professor Potts first, or go direct to that sailor?"
"Why not send a long letter to your friends, telling them what you have told me? You can add that I agree that the photograph resembles you closely, and that you wish to talk the matter over once again with this William Dill."
As impatient as he was, Dave concluded to follow this advice, and a letter of ten pages was sent to Mr. Wadsworth and to Caspar Potts the next morning. In the meantime, it may be added here, Doctor Clay had a closer watch than ever set on Shadow Hamilton's movements, and he also began a quiet investigation of Gus Plum's doings.