"Then who could it have been?" asked Larry.
"That's a hard question, young man," said the carrier. "It might have been any one else. I think it was a person who didn't care about being seen, and didn't want to attract any attention. I guess he would have been better satisfied to have dropped the letter in the box when no one was looking, but seeing me there he came up with it before he knew what he was doing."
"If the letter was from Mr. Potter, and it wasn't the millionaire who mailed it, he must have got some one to do it," the chief clerk of the sub-station suggested, and Larry was forced to adopt this idea. He inquired as to the location of the box at which the carrier stood when he received the missive, and asked in what direction the man came from. Having learned these facts, and deciding he could gain nothing more by staying longer at the sub-station, Larry hurried to the Leader office.
"Well, I've gained something," he said to himself. "I've got a good story, and I have a slender clue to work on. I must write the story first, however. Then I'll go back and tell Grace what I learned."
The account of the letter and the circumstances under which it was mailed created a new sensation in the Potter mystery, and, as on several other occasions, the Leader scored a beat.
As soon as he had finished the story Larry went to see Grace, whom he found anxiously waiting
for him. She asked a score of questions as to what he had learned, and the reporter told her all about his trip to the sub-station.
"What are you going to do next?" she inquired.
"I think I'll go over on the East Side and make some inquiries. Your father may be staying there," answered Larry.
Going downtown in an elevated train, and taking a stroll through that populous section, known as the "East Side," Larry soon found himself in the neighborhood of the box at which the carrier had received the letter written by Mr. Potter. He took a brief survey of the locality.