The boys had arrived back from school, had left their books at the house, and had set out with Chet Morton for a cruise in the motorboat. When Mr. Hardy came back he glanced over his mail and was settling down to read the evening paper when his wife remembered the note that had been left at the door that afternoon. "Some one left a letter for you this afternoon," she said. "I heard the doorbell ring, but when I went to answer it there was no one at the door. I picked up a letter, though, and I put it on your study table." Fenton Hardy went into the study and picked up the letter, slitting open the envelope. Within, was a thin sheet of cheap paper on which had been written a few lines in pencil. He read the message with a slow smile, then handed the paper over to his wife. "Some one trying to scare me," he said. She picked up the note. In a crude, ill-formed hand, she read the following: "_Better give up this counterfeit case or we'll take the shirt off your back. We know this game too well. Let this be a warning to you. Poor Blum is a rank outsider. Better let him go._" Mrs. Hardy looked up anxiously. "What are you going to do about this note?" she asked. The detective shrugged. "Ignore it, of course." "But they may harm you." "They may try. They won't be the first ones who have tried to frighten me away from a case." "But they must be right in Bayport, to deliver a note like this." "I've suspected all along that their headquarters were here. Don't worry, Laura. I'm not afraid of them." "But I _do_ worry. They're desperate men. They'll stop at nothing." Fenton Hardy laughed. "It isn't the first time I've been threatened. It's only a bluff. I'll stay right on the case--although so far I haven't been able to make much progress on it. "But this matter of the note is adding insult to injury, don't you think? First of all they send one of their men around here to fool us to the extent of eight hundred dollars with their counterfeit money, and now they try to frighten me away from handling the case any further." Fenton Hardy looked at the note again, then replaced it carefully in the envelope. "You didn't see any one on the street after the doorbell rang?" he asked. "Oh, there were three or four people walking by, but I didn't notice any of them particularly. They all seemed quite average people. None of them looked at all suspicious." "The chap that delivered the note was probably hiding around the corner of the house until you went inside again. That's their usual scheme. It wouldn't have done much good if you had seen him. Probably some chap they picked up on the street and bribed to slip the note into the door." "I don't like it!"