eturned Captain Raleigh.
"Here, read this," and he passed the lad a slip of paper.

Jack did as commanded. This is what he read:

"Large number of enemy aircraft reported flying over North Sea, fifty
miles south of you, every night. Investigate.

(Signed) "BEATTY."

Jack passed the slip of paper back.

"Well?" exclaimed Captain Raleigh.

"Yes, sir," replied Jack. "You want me to find out what's going on,
sir?"

"Exactly. Can you run a hydroplane?"

"No, sir; but Frank here can."

"Who?"

"Lieutenant Chadwick, sir."

"Oh," said the commander, "so he is Frank, eh? All right. Then here is
what I want you two to do. Take the hydroplane aft and fly south. Take
your time and see what you can find out. The matter may amount to
nothing, and then again it may forebode something serious."

"Very well, sir," replied Frank. "When shall we start, sir?"

"You may as well start immediately. It is hardly possible, judging by
the tone of that message, that you will find anything by daylight, but
at least you can be on the ground by night."

"Very well, sir," said Jack, and waited to see if there were any
further instructions.

Captain Raleigh dismissed the two lads with a wave of his hand.

"That is all," he said. "Report the moment you are able to do so."

The two lads saluted and returned to their own cabin.

"You see," said Frank, "we didn't have to wait very long to find
something to do."

"I see we didn't," agreed Frank. "Now, the first thing to do is shed
these uniforms."

"What for?"

"So that we shall not be taken for British should we fall among the
enemy. We'll put on plain khaki suits."

"Well, whatever you say," said Frank.

This was the work of but a few moments; and half an hour later the two
lads soared into the air in one of the _Queen Mary's_ large
hydroplanes.

"This is something like it, if you ask me," said Frank, as he bent over
the wheel.

"Pretty fine," Jack agreed, raising his voice to make himself heard
above the whir of the propellers and the noise of the engine. "I
wouldn't mind flying all the time."

"Where do we want to come down, Jack?" asked Frank.

"Let's see. The message said the enemy was flying about fifty miles
south. They probably won't be out before dark, so I should say it might
be well to go a little beyond that point."

"All right. But we may miss them in the darkness tonight."

"By Jove! That's so! Funny I didn't think of that. Let me think a
moment."