"Humph! You don't know those boys," said the crabbed instructor sneeringly. "We will go to their room, and find it vacant."
"Wait and see," murmured Frank.
The footsteps approached their apartment. The boys could hardly keep from laughing, but somehow they managed it. So confident was Mr. Callum of finding our heroes out that he did not knock, but entered at once. Frank had been careful to leave the door unlocked.
"Now we shall see!" exclaimed Mr. Callum in triumph, as he lighted the gas. "I will go at once and report to Dr. Doolittle that——"
He stopped in confusion, for looking at him from their respective pillows were the boys he had thought in Dailsburg.
"What—how come you—what are you doing here?" stammered the surprised professor.
"Why, this is our room," spoke Frank innocently. "We always sleep here, Mr. Callum. Did you want us?"
"Want you? You—you—What were you doing in Dailsburg this evening?" he almost shouted.
"Were we in Dailsburg to-night?" asked Frank innocently of his brother.
"Hum!" mused the younger lad, as if trying to remember. "Perhaps we may have been."