Frank snatched the letter from Bob's outstretched hand, and made as if he was about to go in and shut the door. "Wait a minute," exclaimed Hugh. "Here's another." "What kind of a joke are you trying to play on me?" cried Frank angrily. "None at all," said Hugh. "This one is for your father." Frank grew red in the face, "If this is a joke I swear you'll be sorry for it," he exclaimed hotly. "It's no joke at all," said Hugh. "We found this letter lying here under the mat. I was just going to hand it to you." Frank took the letter from Hugh and looked at it suspiciously. Then he turned it over and looked at the back of it. Suddenly he turned pale. Bob and Hugh, watching him closely, noticed this fact, and Bob, suddenly plucking up courage, determined to speak of it. "What does that alligator mean, Frank?" he asked. The color rushed back into Frank's face. He looked as though he were going to run. He swallowed hard two or three times, choked, and then swallowed again. "I don't know," he blurted out finally, and stepping inside slammed the door shut in the faces of the two boys. Hugh looked at Bob and smiled. "Frank was certainly glad to see us, wasn't he?" he said sarcastically. "I should say so," Bob agreed. "Let's go home." They went down the steps and walked slowly in the direction of the Cook home. "Frank's a queer fellow," said Hugh finally. "He certainly is," Bob agreed. "Do you think he knows what has happened to his father?" "I doubt it. I don't believe he would have been so surly if he had known." "What do you think about the alligator?" "I'm sure I don't know," said Bob. "It must mean something though, and Frank must know what it is. Did you see how pale he got when he saw it!" "Maybe it's the sign of some secret society like the Black Hand, or the Ku Klux Klan, or something like that." "Still I can't understand why they should send a warning to Mr. Wernberg if he is a member of the gang." "It may not have been a warning," said Hugh. "Perhaps it was just a message of some kind or another." "Then why should Frank have been so scared when he saw it?" "Don't ask me. I'm getting more mixed up every minute." They turned into the Cooks' yard and slowly approached the house. A man and woman were just disappearing around the corner. "Who are they?" Hugh inquired. "Lena, the cook, and one of her beaux," said Bob. "I thought Heinrich was in love with her." "He is," laughed Bob, "but he has a rival, and that's the man." "What's his name?" "Karl Hoffmann." "Another German," said Hugh soberly. "Say, Hugh," laughed Bob, "you certainly are suspicious. You suspect good old Lena, and now you suspect the man with her because he has a German name. Why, that man Hoffmann has worked for father for years, and father thinks the world of him." "That doesn't mean he may not be mistaken," Hugh insisted.