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.