"Of course; but he's not telling everything he knows."

"But doesn't Lord Hastings know?"

"I suppose so; but he is keeping his information to himself."

"Well, I didn't know any of them had disappeared."

"They have, though, and I heard Mr. Churchill say that the government
hoped within another month to have rid British waters entirely of the
German submersibles."

"I hope his hope comes true," said Frank with a smile.

"And I; but I would like to know something more of the mystery of these
vanishing submarines."

Both lads were to learn something more, even sooner than they could
possibly have hoped.

The door opened and a man strode into the room. Attired in the full
uniform of a British naval commander, he made a striking appearance in
his gold and lace. He greeted the two lads with a smile.

"Well, boys?" he said.

The newcomer was Lord Hastings, erstwhile distinguished secret service
agent and new commander in his British majesty's royal navy. Also,
though the fact was known to few, he was a distant cousin of the king
himself and one of the most highly trusted officers of the empire.

"Well, boys?" he repeated.

"Well, sir," said Frank, "we were just discussing the mystery of the
vanishing submarines."

Lord Hastings gazed at the lad in surprise.

"Vanishing submarines!" he repeated. "And tell me, how did you know
there were such things as vanishing submarines?"

"Why, Jack told me, sir," replied Frank.

"And how did you know it?" demanded Lord Hastings of Jack.

"I heard you and Mr. Churchill discussing it, sir," replied Jack.

Lord Hastings drew a long breath, evidently of relief.

"I didn't know we had been so indiscreet," he said, half to himself.
"However, there is no harm done, for I know you boys are to be trusted
not to repeat what you overhear. I'll tell you this, you two are among
the very few who know that any of the German submarines have been
accounted for."

"Then it is true?" asked Frank.

"Oh, it's true enough," replied Lord Hastings. "Perhaps a hundred of
them have disappeared."

"And where are they, sir?" asked Frank. "At the bottom?"

"That," said Lord Hastings with a slow smile, "is the mystery the German
government would like to solve."

"But surely you know, sir."

"If I did, I would not repeat it within these four walls," declared Lord
Hastings. "Walls have ears, you know, as is proven by the fact that Jack
overheard my conversation with Mr. Churchill."

"I