"I am always sure," was the tart response.
Hatch opened a small handsatchel and removed several queerly wrought tools. These he spread on the roof beside him; then, kneeling again, began his work. For half an hour he labored in the gloom, with only the flashlight to aid him, and then he rose.
"It's all right," he said.
The Thinking Machine examined the work that had been done, grunted his satisfaction, and together they went to the skylight, leaving a thin, insulated 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.
They went along the hall to a room in the rear, 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 on. 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 someone might pass this way and disturb it. You take the spool, go back to the roof, winding the wire as you go, then swing the spool down to me over the side of the building, so that I can bring it in through the window. That will be best. I will catch it here, and thus there will be nothing to indicate any connection." Hatch went out quietly and closed the door.
Twice the following day The Thinking Machine spoke to the financier over the telephone. Grayson was in his private office, Miss Winthrop at her desk, when the first call came.