lated wire behind them stringing along to mark their path. They passed down through the roof, and into the darkness of the hall of the upper story. Here the light was extinguished. From far below came the faint echo of a man's footsteps as the watchman passed through the silent deserted building.
"Be careful!" warned The Thinking Machine.
Along the hall to a room in the rear they went, and still the wire trailed behind. At the last door they stopped. The Thinking Machine fumbled with some keys, then opened the way. Here an electric light was going. The room was bare of furniture, the only sign of recent occupancy being a telephone instrument on the wall.
Here The Thinking Machine stopped and stared at the spool of wire which he had permitted to wind off as he walked, and his thin face expressed doubt.
"It wouldn't be safe," he said at last, "to leave the wire exposed as we have left it. True, this floor is not occupied; but some one might pass up this way and disturb it. You take t
