"'Smatter!" exclaimed Budge, that being his short-hand way of stating that was what was the matter. "A spark plug from an automobile," mused Jack. "Well, that doesn't seem to give me much of a clue." "Gotermobe?" asked Budge. "No, of course I haven't an automobile," replied Jack. "Knowoas?" "Do I know who has? Why--By Jove! I believe I see what you mean. Say, it's lucky you found this. I'll turn detective for awhile now. I wonder how this got into Grimm's room." "Rolled under door, I guess," replied Budge, speaking more rationally as he threw away his cud of gum. "From hall, maybe." "That's it!" exclaimed Jack. "I see it now. Thanks Budge. I hope I succeed. I'm much obliged to you." "'Sallright!" exclaimed Budge, as he hurried away to attend to some of his duties. When Jack got back to his room he found quite a gathering of his chums there. "In for it on account of that Klu-Klux business?" asked Sam Chalmers. "Not exactly that," answered Jack, "though if I'd stayed at home It wouldn't have happened." "Ha-ha-ha-has it g-g-gg-got anything t-t-t--" began Will Slade. "Whistle it!" exclaimed Bony Balmore. "Sing it!" came from Fred Kaler. "Here I'll help you out," and he began to play on his harmonica. "Whole-wheat-whangdoodles!" cried Nat Anderson, "but tell us, Jack. Don't keep us in suspense." "It's the bell," said Jack. "I'm accused of taking it down and putting it in Grimm's room. They found a rag with arnica on it near the ding-dong, and Old Grimm jumped to the wrong conclusion, basing his belief on what he saw here last night in the first-aid-to-the- injured line. I've got until to-morrow to prove that I didn't do it." "We can prove it easily enough," said Sam. "Not so easily as you think," spoke Jack. "Grimm saw us out late, you remember, and if all of you joined in saying it wasn't I who did it, they wouldn't believe you. I guess they want to make an example of someone. No sir, I'm going to do some sleuthing on my own hook. I've got a good line and a bit of evidence to start with. I'm pretty sure I can make some folks around here sit up and take notice about this time to-morrow." "Good for you, Jack!" exclaimed Dick. "If you want any help call on us!" "Thanks," replied Jack. "Now I guess we'd better get ready for breakfast." His chums left him to complete his dressing, and, when they were gone, Jack carefully laid aside the spark plug Budge had given him. "First link," he said. During the noon intermission Jack had a short but earnest talk with Socker, the school janitor. The latter nodded his head vigorously several times during the conversation. "I'll get it for you," he said as he and Jack parted. At the close of school that afternoon the janitor went to Jack's room with a large bundle. "Any trouble?" asked our hero. "Not a bit," replied Socker. "He was out and I found it rolled up in a corner, just where he had thrown it. He hasn't even cleaned it."