Just what was done was not disclosed, but it leaked out that a close watch was being kept on all the employees at Yale, and suspicion, it was said, had narrowed down to one or two. One day Link called on Andy to pay back the money he had borrowed. "There's no hurry," said Andy. "I don't need it." "Oh, I want to pay it back," said the young farmer. "I have plenty of cash now," and he exhibited quite a roll of bills. "Been drawing your salary?" asked Andy, with a laugh. "No, this is a little windfall that came to me," was the answer. "A windfall? Did someone die and leave you a fortune?" "No, not exactly. It came to me in a curious way. I got it through the mail, and there wasn't a word of explanation with it. Just the bill folded in a letter. A hundred-dollar bill, it was, but I had it changed." "Do you mean someone sent you a hundred dollars, and you don't know who it's from?" asked Andy, in surprise. "That's right!" exclaimed Link, with a laugh. "I wish I did know, for I'd write and thank whoever it was. It surely came in handy." "Why, it's very strange," spoke Andy, slowly. "Could you tell by the postmark where the letter came from?" "It was from New York, but I haven't a friend there that I know of." "Well, I'm glad you've got it. Take care of it, Link." "I intend to. I can lend you some now, if you need it, Mr. Blair." "Thank you, I have enough at present." Andy watched his protege walk across the campus, and near the middle observed him stopped by a stranger. Link appeared surprised, and started back. There was a quick movement, and the young farmer was seized by the other. "That's queer!" exclaimed Andy. "I wonder what's up? Link may be in trouble. Maybe that fellow's trying to rob him." The quadrangle was almost deserted at the time. Andy hurried down and ran over to where Link was standing. The student caught the gleam of something on the wrist of his friend. It was a steel handcuff! "What--what's up, Link?" Andy gasped. "Why, Mr. Blair--I don't know. This man--he says he's a detective, and----" "So I am a detective, and I don't want any of your funny work!" was the snappish retort. "There's my badge," and it was flashed from under the armhole of the man's vest, being fastened to his suspenders, where most plain-clothes men carry their official emblem. "A detective!" gasped Andy. "What's the matter? Why do you want Link Bardon?" "We want him because he's accused of being the quadrangle thief!" was the unexpected answer. "Stand aside now, I'm going to take him to the station house!" CHAPTER XXX THE LETTER Andy could scarcely understand it. Surely, he thought, there must be some mistake. He was glad there was not a crowd of students about to witness the humiliation of Link--a humiliation none the less acute if the charge was groundless. "Wait a minute--hold on!" exclaimed Andy, sharply, and there was something in his voice that caused the detective to pause.