"I know all about it," the watchman answered. "The foreman left instructions for me. We're crating automobile ambulances for shipment to France. I want to show you something that we found today."
He led the way into the stevedoring shop, there to point out the axle of a great chassis—and to swear quietly as he looked at it.
"German spies done it!" he announced. "Nobody else would have been so dirty and low. These are ambulances, y'know—ambulances for use on the battlefields. And you know what'd happen if that ever got on a shell-torn field."
He pointed to the axle of the car. There, where the putty had been removed by the workmen who had discovered it, was a great, jagged hole in the steel of the axle, a hole burnt by an acetylene torch, converting the axle into a weak, shallow shell, doomed to break with the first holting strain. Grant frowned as he looked at it.
"So that's the game, eh?" he said. "That's why so many ambulances have been breaking down in France! That's why—"
He turned sharply, the watchman with him. Far at one side of the opposite dock they had seen the shadow of a man as it slunk along, hiding behind the boxes and bales as he made his way from light to darkness. Grant sped forward, the watchman beside him. A moment more and the shadow leaped forth, to seek escape in the maze of shipping on the docks.
But impossible. Headed off by closed doors, he veered, dodged, swerved in his course and leaped past the guard of an interned liner, seeking to spring from it to the next in his effort to escape.
An effort that failed. Blocked again, he veered once more, crashed his way through the door of the ship's wireless room, then whirled, a chair lifted high over his head. But the blow: did not descend. The tactics of the football field had come into play for Grant—and with a quick motion he had blocked the blow of the spy, disarmed him and forced him against the wall. Fifteen minutes later, he was listening to the confession, forced in jerky sentences from the spy's lips:
"A guy gave me $100. to set fire to the docks," he was saying. "That's all I know. He was some fellow who worked around the waterfront here. I'd gotten a lot o' money offen him and I wanted more. I belonged to his magneto and axle gang."
"His what?" Harrison Grant bent forward.