"We're supposed to be changing some electric light switch boxes, you and I. That is, if we're caught. You're my helper. No breaking in or anything like that. Got the key from the owner. But if they come down, that tall one and the short one, they might get a little rough. See? Question is, are you still with me?" he concluded. "Hundred per cent!" There was no hesitation in Johnny's tone. For all that, there was a sense of dizziness in his head. He was seeing again the living skeletons, one with a knife on its hip, the other with a blade hanging from its bony fingers. "All right," said Felix, "let's go!" "But why should we change the switch boxes in that place?" Johnny asked. "Rule one of our clan is, 'No questions asked'!" Felix chuckled. A moment more and a key turned in a lock. They found themselves in an ancient parlor. The place was dark and silent, reeking with mystery. "Here you are." Felix handed Johnny a large flashlight. "Just focus that on my hands while I work. Won't try to raise the shades. Might disturb our friends upstairs. Might--Sh! Listen!" The red-haired boy backed against the wall. Involuntarily Johnny gripped the handle of a hammer with his free hand. The memory of a knife blade protruding from a sleeve was fresh in his mind. For a space of seconds the two boys remained motionless. "Thought I heard something." Felix moved forward. A moment more and his long capable fingers, trembling slightly, were busy removing an electric punch button from the wall. "Good!" he whispered. "Hole's large enough." Diving into his kit, he brought out a small metal box wrapped about with wires. After unwinding these wires, he stood again at attention. Catching no sound, he resumed his work. Pushing the wires through the hole left by the removal of the punch button, he slid them down between the walls, then prepared to fit the black box into position. "Perfect," he sighed. "Couldn't have been better! I--" He held up a finger for silence. There had come a faint sound from above. "Like a bare foot touching the floor," Johnny thought. Once more he gripped his hammer handle hard. If they were attacked he would do his bit. But would that be enough? Strange business this! A chill crept up his spine. Felix resumed his work. His fingers flew. "There!" he sighed. "They'd never know a thing has been changed. And yet--" A moment later he disappeared into the depths of a large closet. What he did there Johnny was not permitted to know. For a full quarter of an hour, alternately chilling and thrilling at every sound that reached his ears, Johnny stood there on guard. "Now," the other boy at last whispered in his ear, "we go this way." They passed through a door and down a stair into a cellar dark as night. "One minute here, and then for the outer air." Felix moved forward cautiously. For all that, his foot struck some object that gave forth a low, hollow roar. At the same instant there came from above an unmistakable sound of movement.