to me like this. He was always afraid of people forging his name to letters and notes like this and perhaps getting papers or information that they shouldn't. So we arranged this sign that he would always put beneath his name."
Frank snatched up the note again.
"And there's no sign here. Just his signature."
"It may be his signature. If it isn't, it is a very good forgery. And it may have been that he forgot to put in the secret sign, although it isn't like him to do that."
Mrs. Hardy was plainly worried.
"If he didn't write it, then who did?" asked Joe.
"Your father has many enemies. There are relatives of criminals whom he has had arrested and there are criminals who have served their terms and have been released. If there has been foul play the note might be meant to keep us from being suspicious and delay any search."
"Foul play!" exclaimed Frank. "You don't think something has happened to dad?" he added, his face showing his alarm.
"The fact that he didn't put the secret sign underneath his name makes me anxious. What other object could any one have in sending us a note like that, if not to keep us from starting a search for him?"
