"But how can they remember when they must handle thousands of letters every day?" "Perhaps they cannot, but it is worth trying. You see in that section of the city are mostly foreigners, who write a peculiar hand, and use stationery anything but clean or of this quality. This envelope and paper are of an expensive kind." "Yes, they are some father had made to order for his private correspondence. I did not know he took any to Europe with him, but he must have." "It may be that a letter carrier or mail sorter took enough notice of the envelope to remember it," Larry went on. "Besides there is a small blot on it, and the way in which the stamp is put on shows that some glue or paste was applied to the envelope. Probably he used an old stamp which had no mucilage on. To make it fast to the envelope your father, or whoever posted the letter, would have had to use some sticky substance, and, in doing so, he has put it on a little too thick. Some spread out from under the stamp and soiled the envelope. "Of course the sorters and carriers don't pay much attention to the pieces of mail, except to see that they are properly stamped and addressed, but it's worth trying. This envelope would attract attention if anything would." "And you are going to use that for a clue?" "I'm going to try. It may be useless. If we can find in what particular locality it was mailed we can have the police keep a watch for your father. He may mail other letters there." "But my father is not a criminal. Why should the police watch for him so particularly. They are keeping a general lookout now, but I wouldn't like to think they were lying in wait for him." "It's the only way to find him," said Larry. "Of course it's unpleasant, but there is evidently some mystery here, and that's the best way to clear it up." "But he says he has to stay away for a while," argued Grace. "Maybe he wouldn't like to be found." "Of course that point has to be considered," Larry admitted. "But I take it you and your mother want to find your father, or be in a position to communicate with him." "Oh, we do!" exclaimed Grace. "Then we'll have to ask the police to help us. There is no disgrace in it. Everyone knows your father is honorable, and if he wants to disappear that's his business. It is also perfectly right for you to try to find him, for----" and Larry stopped. "Well, for what?" asked Grace, seeing the reporter hesitate. "I don't want to alarm you," Larry went on, "but I was going to say that there is no way of telling but what some one may have imitated his writing and forged his name." "I am sure that is my father's writing," the girl said, earnestly. "Of course I may be mistaken. I hope not. I prefer to believe that note is from him. It makes me happier." "Of course there is only the barest possibility that this note is not from your father, but we can take no chances. That is why I want to make a systematic search, beginning at the sub-station."