Dr. Mann could see it. There was unquestionably a dead rat; and the ink spilled on the floor, the jar knocked from the mantel, the disordered furniture, scattered books, and the excited faces of the boys attested the fact that the poor animal had not been an expected guest. "Who could have played such a contemptible trick!" exclaimed the teacher, in disgust. "Did you see who threw it in?" "No, we were studying at the desk, and some one opened the door so quietly we didn't notice it, and chucked the thing right at us." "Strange!" mused Dr. Mann. Strange, indeed! Yet after all not so strange to one who possessed the key. Rob held rolled in his hand a slip of paper which he had taken from the floor during the discussion. He glanced at it furtively as he stood listening, and smiled an involuntary and promptly extinguished smile as he read the expected legend, "The Third Plague." Even Dr. Mann might have formed a fairly accurate suspicion if he had considered the manner of the twins. Here was no wondering indignation, no loud invective against an unknown perpetrator, but the sullen bitterness of those who nourish a personal spite. But Dr. Mann, learned in ancient lore, had but slight knowledge of boys. "I can't understand it," he said at length. "The matter must be looked into. It shows a sad misunderstanding of the Seaton spirit. One of you will please carry the animal to some proper place, and then perhaps we may have quiet again." Duncan volunteered for this duty, and Dr. Mann and Owen retired. The latter reappeared, however, as soon as he heard Duncan's step on the stairs, in order to deliver the paper which he had secured. "Oh, you had it!" exclaimed Duncan, as he read the label. "I thought it must be somewhere. Seven more! Gee whiz! I don't believe I can stand it." "You'd better come to terms with him," said Owen. "I wish we could," sighed Duncan, "but Don's got his back up and he will never give in. This living in perpetual fear of your life is wearing. I always pull my bed to pieces every night to make sure there isn't anything there, and I never can get it together tight again. Go and see him, won't you, and see what he says." Owen grinned. The prospect of acting as intermediary pleased him. "All right," he said cheerfully. "What terms do you offer?" "None," replied Duncan. "Just sound him and get his terms. And don't say we sent you." Duncan returned to his room and Owen knocked at Payner's door. "Who's there?" demanded the cautious inmate. "Owen." "Any one with you?" "No." The door was unlocked to admit Rob, the catch being immediately snapped behind him. "'Fraid of burglars?" asked Rob, facetiously. "'Fraid of something, sure enough," replied Payner, quietly. "You can't be any too careful in this place." "Payner, how long are you going to keep this thing up?" asked Rob, coming with most undiplomatic directness straight to his point. "What up?" "Oh, all this plague business,--eels and guinea pigs and rats."