“I have found the trouble, Captain Hardwick,” the chief electrician reported, when he was alone with the captain in the cabin. “There it is,” and he laid the bent nail before his commander.

“You look half sick, Sparks,” said the latter, looking at him keenly. “Be careful of yourself.”

“It’s that wretched cold I got from my ducking at Cape Cod,” laughed the chief electrician. “I’ll be all right soon.”

The captain picked up the nail and examined it curiously. “Well?” he said inquiringly.

“That was in the grounded coil,” said the chief electrician. “That is what grounded it. Some one drove that nail into the coil.”

The captain stared at the nail long and fixedly. “It beats me,” he said at last. “You think that it was done maliciously, don’t you? Is there a possibility that it might have been done in an experimental way? Now, young Harper is very ambitious and desirous of learning. Might he have been experimenting, trying to learn something, by fooling with the outfit?”

“In my opinion, Captain, whoever did this did it with perfect knowledge of what would happen. I cannot think it was done for any purpose except to put the wireless out of commission.”

The captain frowned. “I fear you are right, Sparks. But who would want to put the wireless out of commission? I can think of only two reasons why any one should do that. Some one might have it in for me or for the operator. If it weren’t that young Black was asleep when this was done, I’d think he did it. You know he and Harper had some words.”

“That would explain everything,” said the chief radio man, “but the facts won’t fit the case.”

“So far as we know, not a soul was on deck except the men on watch. If some one entered the radio room while Henry was up in the chart room with me, he would have had to be both sly and slick. He would have had to watch young Harper’s every movement, and be all prepared to run in and drive this nail home. It was a terrible risk to run, for it was certain that the wireless man wouldn’t be away from his key for more than a minute or two. Discovery was almost certain. The more I consider it, the more it seems to me that young Harper must have been experimenting. Did you find anything else out of its usual order?”