"Ha!" cried the professor. "I see it now. You are trying to play a joke on me, with the aid of Clinton and Parsons. But you shall all three suffer for it! I _will_ knock on that door. I _will_ confront your fellow conspirators with the evidence of their silly act. Come here," and he placed his hand on Phil's shoulder and led him toward the room of the three chums. "You shall not trifle with me!" he added fiercely.