"Oh, boy!" he giggled. "The expression—on your—face—!" Then he was away again, leaning across the window-sill weakly, shaking with laughter.

Jerry Gilroy tiptoed quietly up behind him. A quick movement and he lowered the window until it was against Chet's back.

The practical joker suddenly stopped laughing, and turned his head.

"Hey! What's the matter?" he inquired.

He was pinned down by the window and he could not see Jerry picking up the flat piece of board that had been the instrument of torture a few minutes previously. But a suspicion of the truth came to him, and a roar of laughter from the other boys warned him that vengeance was due.

It came.

Smack!

Chet Morton wriggled and squirmed, but he was pinned helplessly by the weight of the window against his shoulders, and he presented a more tempting target for Jerry's ministrations with the flat stick, and a more stationary target as well, than Jerry had presented for him.

Smack! Smack! Smack!

He roared with pain and, helpless as he was, danced vainly on the floor in his efforts to escape. Jerry Gilroy belabored him across the rear with that stinging stick until his desire for revenge had been fully satisfied, while the other boys howled with glee at the manner in which the tables had been turned.