"Have you got 'em in paper bags?" asked Ned, as he began to open the box he carried.
"Sure," replied Bart, and the others answered in the affirmative.
"When I open the grating just toss the bags out, right in the middle of the floor," Ned went on. "Do it quick, as I want to close the ventilator before they see where the things come from."
An instant later Ned had opened the ventilator grating, which he had previously loosened. Then, through the air, went sailing four paper bags. They struck almost in the middle of the ballroom floor and burst.
Then from the bags there scampered over three score mice, rushing, running, leaping and darting amid the dancers, with frightened squeaks and squeals.
For a moment there was silence, broken only by the noise of the rodents. Then every girl in the room, and there were forty of them, uttered a frightened scream and rushed for a place of safety.
"A mouse! A mouse! Oh, save me!" was the universal cry, and the music came to a stop in a crash of discord as the dance was most effectually broken up.
CHAPTER VIII
FRANK IS WARNED
All over the room ran the mice, and all about darted the frightened girls. The boys were, at first, too surprised to know what to do, but, at a rallying cry from someone, they started after the mice. However, they had no weapons to kill the rodents with, and had to be content with taking kicks at them as they darted past, seeking means of escape.
"Couldn't have worked better!" exclaimed Bart, as he and his chums watched the scene from where they were hidden.