The dancers accordingly arranged themselves in a long line and walked single file past the teacher. She saw only girl's faces, however, as she peeped under the masks, and the dance proceeded. The next disturbance came when the maskers had all taken their stand at one end of the room at the request of the six dominoes, who managed to whisper to each sophomore that there was presently to be a surprise. An expectant hush fell over the company as the six dominoes filed out of a side room and stood, for a moment, in full view of the sophomores. Then the six deliberately lifted their dominoes, disclosing trouser legs and men's shoes. Instantly the place was in pandemonium; yet before the sophomores could rush upon the intruders six long horns were blown in unison, and immediately the lights went out. In the darkness the six dominoes made for the stairs, rushed along the gallery, and were admitted to the laboratory by the duplicate key. But, just before the blue domino disappeared, she called out in a loud voice from the gallery: "The freshmen are avenged!" When the doors were safely closed the lights were turned on again, disclosing the sophomores blinking foolishly at each other after the sudden startling change from darkness to light. "They are in the laboratory!" cried one. "Let's cut off their escape!" The angry sophomores made a rush for the door. "Hurry girls!" urged David, who had just returned to the laboratory after manipulating the lights. "They'll catch us before we know it." But the young fugitives were too late. Just then there was the sound of many feet running up the stairs from the other door. "How about one of the gallery doors?" asked Grace. "They are all locked," answered David. "There only remain the skylight trap-door and the roof. Do you think you could manage it if I helped you?" "Of course; we could manage anything," protested the freshmen girls. It was an easy matter to climb up the ladder, and clamber through the trap-door on to the roof. "We're just in time," whispered David. "They have found the right key to the gallery door, and they'll be coming in both ways. Crawl carefully now, girls, for heaven's sake, and don't slip!" The seven young people began slowly to draw themselves along the gymnasium roof on their hands and knees. Fortunately, it was not a very sloping roof, and their only danger lay in their movements being heard from below. Meanwhile the gymnasium had emptied itself, and parties of enraged sophomores were engaged in searching the adjoining class rooms and passages. "Let's surround the building on the outside," cried one of the class leaders. "They can't escape, then, by any of the fire escapes, and we are sure to catch them!" In a few moments, David peeping over the edge of the roof, saw figures stationed at every possible exit, waiting patiently. "Lie low," he whispered, "and crawl on your stomachs, or you're surely caught."