"She's fine," replied Frank. "She said there'd be something special for supper to-night, seeing you're back."
"Good! And what have you two been doing? Kept out of mischief, I hope."
"Well, we've kept out of mischief," said Joe; "but we haven't kept out of trouble."
"What's the matter?"
"We just got fooled by a smart stranger who stepped off the express. It cost us five dollars."
"How did that happen?"
"He asked us to change a five dollar bill for him—"
"Ah, ha!" exclaimed Fenton Hardy, raising his eyebrows. "And what then?"
"It was counterfeit."
Mr. Hardy looked grave.
"Have you got it with you?"
"Yes," answered Frank, producing the bill. "I don't think we can be blamed such an awful lot for being fooled. It certainly looks mighty like a good one."
Fenton Hardy put down his bag and examined the bill closely for a moment. Then he folded it up and put it in his waistcoat pocket.
"I'll take care of this, if you don't mind," he said, picking up his bag and beginning to walk toward the station exit. "As it happens, I know something about this money."
